In the Jewish religious texts the numbers 7 and 40 seem to appear quite often and carry special significance. Some examples among many:

  • God's creation lasts 7 days
  • The Great Flood was from rain falling for 40 days and 40 nights
  • Noah brings 7 pairs of every kind of animal he can find
  • Moses wrote the Ten Commandments over the course of 40 days and 40 nights
  • Debts are cancelled every 7 years

And so on and so on.

I am curious as to natural explanations as to why these two numbers came to hold such significance. I'm not interested in how these numbers are represented as holy numbers in Jewish texts, but rather thoughts, theories, or (ideally) knowledge on why people living thousands of years ago came to attach such significance to these two numbers.

My presumption is that the number 7 has long been regarded as special by many cultures due to the fact that there are 7 heavenly bodies visible to the naked eye: the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn. For instance, the names of the days of the week correspond to these seven heavenly bodies.

But I am uncertain as to where or how or why the number 40 would have gained such significance.

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    In Hebrew, the names of the days of the week, literally translated, are "first day, second day, third day ... Sabbath". The phenomenon of the names of the days of the week corresponding to heavenly bodies is something that is more a feature of English (and its ancestor languages). – Yaakov Ellis May 14 '11 at 20:15
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    You're asking on a site "for students and teachers of Jewish law and tradition" for "why people living thousands of years ago came to attach such significance" irrespective of "how these numbers are represented as holy numbers in Jewish texts": essentially, to ignore Jewish law and tradition and assume that the holy texts comprising such use 7 and 40 as a cultural thing? Sounds rather insulting to the holy texts and off-topic on the site. Perhaps,though, I'm misinterpreting the question, in which case I'd love to be set straight. – msh210 May 15 '11 at 4:14
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    @msh210: I apologize if it comes across as insulting, as I don't mean it to. From my understanding, there is a lot of emphasis on numbers and numerology in the Torah, from certain numbers repeating often (7 and 40 being two prime examples) to multiples of these numbers. I'm curious if there is an explanation to the importance of said numbers beyond, "God said so." It would be like asking, "Is there a societal explanation to forgiving all debts every seven years aside from God commanding it?" Is that insulting? I don't think so and, to me, it seems inline with "Jewish tradition." – Scott Mitchell May 15 '11 at 20:41
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    I think that the objections to the question are not to the search for natural phenomena that are related to 7 and 40, rather they are to @Scott's comment below: "why would a group of people living thousands of years ago come to hold these two numbers in such significance" as well as in the question: "natural explanations as to why these two numbers came to hold such significance". The phrasing in both places implies an assumption that items of spiritual significance in Judaism would get that significance from nature, and not from God (a sentiment that many here would find objectionable). – Yaakov Ellis May 16 '11 at 11:07
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    @msh210: I admit my knowledge in this area is essentially none outside of what I've read from the Old Testament, so please do forgive my ignorance. I guess my underlying question then is does the Chinuch give any reasoning behind the significance of the numbers of 7 and 40? – Scott Mitchell May 16 '11 at 15:46

7 is the length of time for a natural cycle to transpire, often ending with holiness/sanctification of some sort (the pattern set by creation)

  • Seven days to the week (cycle of days) (and notably, seven times seven weeks from Passover to Shavuot, during which time the Jewish people transformed from a group of slaves into a nation at Mt. Sinai)
  • Seven years for a sabbatical cycle (debts canceled, among other things; and seven times seven years to a Jubilee)
  • Seven days of mourning
  • Seven days for an impure person to go achieve purity
  • Seven branches to the Menorah (cadelabra) in the temple
  • Seven days for the festivals of Sukkot and Passover

(And parenthetically, this leads to the number 8 being associated with new beginnings, after having finished the cycle of seven: circumcision, becoming pure after the seven days of the purity cycle, beginning of a new week, etc).

40 is the amount of time for allowing a complete birth/rebirth:

  • According to Jewish tradition, it is the amount of time that it takes a fetus be recognized, the gender of the child set
  • The great flood - rebirth of the world the sinful behavior into which it had sunk in the previous generations
  • 40 days for Moses to receive the Torah (more than just the 10 commandments) - the ultimate birth of the Jewish people (for both the first and second sets of tablets, with a 40 day period of praying for forgiveness in between)
  • 40 years in the wilderness after leaving Egypt before entering Canaan (Israel)
  • 40 measures of water needed in a mikveh (pool used for achieving ritual purity - allowing for the transformation of a person from impure to pure states)
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    Thank you for your answer. Unfortunately, my question was poorly worded. (I've since edited it.) I'm actually more interested in natural explanations as to how these numbers became significant, not why they are significant. In short, why would a group of people living thousands of years ago come to hold these two numbers in such significance? From a religious context you could say, "Because God created the Earth in 7 days, the Great Flood lasted 40 days, etc." but I'm more interested in ideas as to natural contexts. – Scott Mitchell May 14 '11 at 19:46
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    WADR, your question presupposes that there are natural explanations for why certain numbers are more significant than others, explanations which are divorced from a religious context. Very often with Judaism the ultimate answer is "because God said so". We do not believe that a group of people living thousands of years ago invented this Judaism, and as such, would obviously have based significant numbers off of natural events. The belief that the Torah came from God leads to a divergent path from one where each item of significance must have a natural explanation. – Yaakov Ellis May 14 '11 at 20:13
  • I guess that is my question, then: Are there known natural explanations for the significance of these numbers or is it just, "God said so?" It sounds like you would contend that the answer to my question falls in the latter camp. – Scott Mitchell May 14 '11 at 20:57
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    @Scott: I am not saying that there are no natural phenomenon that could correspond to those numbers and provide what may be a satisfying explanation. I just think that if there was, I would say "that's nice, but so what?". Because the answer (in the context of this site) is that the importance of these numbers is of divine origin, so natural phenomenon that might have led people to create a religious system that featured these numbers are not really of any consequence. – Yaakov Ellis May 15 '11 at 6:20

I don't know if you'd consider this a "natural" explanation, but...

Kabbalistic sources speak of ten basic modes through which G-d relates to us, called sefiros. These are described in terms of three intellectual and seven emotional attributes (and indeed, they are the spiritual sources of these thoughts and emotions as we experience them). The seven "emotional" sefiros, then, in their various combinations and permutations, make up the complete gamut of how we experience G-d's presence in our world (and also how we relate to each other).

Further, these same sources describe four progressive spiritual "worlds," in each of which G-dliness is more and more concealed; the last of these is our own world, where G-d's presence is barely recognizable - the universe appears to function on its own without a Creator at all, G-d forbid - and it takes considerable thought to see the truth behind the natural order. Each of these four "worlds" has its own version of the ten sefiros, again progressively coarsened until they assume the forms with which we're familiar.

Thus, to echo Yaakov Ellis's point, the underlying reason why 7 represents a natural cycle is because in terms of the sefiros, 7 is a complete group of them (the three "intellectual" attributes find their expression through them, just as in a human being, one's intellectual ideas have to be mediated to others through one's emotional qualities). So, for example, each day of the week reflects a different "emotional" mode in which we relate to G-d and He to us; similarly, each day of the mourning period is meant for a person to process their grief through the prism of that day's sefirah attribute; and so forth.

Forty is, again as Yaakov noted, a number representing complete transformation. This is arrived at by taking the total number of sefiros in all four stages of their spiritual evolution through the Four Worlds - in other words, the total number of (describable) ways in which we perceive G-dliness. (Here both the "intellectual" and the "emotional" sefiros come into play, because they are both co-equal parts of the human psyche and of its spiritual source/analogue.) Thus, for example, to receive the Divine Torah, Moses had to spend forty days transforming all of these forty aspects of himself and his relationship with G-d, literally becoming a new man in the process. So too, an impure person immerses in a pool of 40 se'ah of water (and the earth, during the Flood, had to undergo that number of days of cleansing with water), and comes out as a renewed being.


To answer your question directly:

7 is the number of visual celestial bodies seen from earth without the aid of a telescope. The Sun, Moon, Saturn, Jupiter, Mars, Venus and Mercury.

40 is the number of weeks of the average pregnancy, which likely adds to the meaning of 40 in Judaism as being a time of full gestation for a change to occur.

However, I'm curious why you only ask about 7 and 40. There are a few "magical numbers" in the Bible.

1, (2?), 4, (5?), (6?), 7, 8, 10, 12, 40, and 70 all have significance. One can speculate about why these numbers are chosen, but really they are just speculation. The numbers with ? next to them are of limited significance, or are very significance in larger multiples (such as 600,000)

The question then, is 10 a combination of 5 * 2? is 40 just 10 * 4? 70, 7*10 ? Then, why multiplication? maybe 10 is 7 + 3, and 40 is 12 + 10 + 8 + 7 + 3? The speculation is truly endless.

Edit: In response to Scott below, Numbers and their usage:

  1. God is declared 1 in the Shema, and is mentioned in the 10 commandments., Israel is also called an "Am Achad"

  2. Heaven and Earth are called to be witness. The Torah is full of "couplets" which are used to compare /contrast, as well as to emphasize a particular law.

  3. There are four types of redemptions mentioned, 4 mothers, 4 ways we are told to give over the story of Egypt, Jews are promised to be scattered to 4 corners of the earth, The tribes when travleing in the Desert are divided into 4 groups, as well as during the census. There were four flags created for the camps as well.

  4. Abraham's coveneant of the parts, is done with 2 rows of 5. The torah is divded into 5 sections, The 10 commandments are often divided into 2 rows of 5.

  5. Seven days of the week, seven years of shmitah, 7 weeks counted after Pesach for the Omer, 7 days of Sukkot and Pesach, 7 kosher animals on the arc, Some sacrifices are done in groups of 7.

  6. Eight, is used for the Bris, 8 is the only digit not to appear in the census, In the book of Vayikra, from parshat Shemini, to Achrei Mot, the number 8 is used often. 8th day of the festivals, 8th day for the bris, The priests go to the mikveh on the 8th day to purify Tumah. There is a special holiday after Sukkot translated as "8th day of gathering"

  7. 10 commandments, 10 Plagues, 10 spies reject Israel, 10 statements in creation.. (And the Mishna has lots of other lists of 10s) Leaders are set over groups of 10 (and 50, 100, and 1,000)

  8. 12 tribes, 12 stones, 12 sons (which are different than the 12 tribes), The Temple is said to be built 480 years after the exodus (12 * 40)

  9. 40 years in the desert, Moshe's live can be divided into 3 phases each which lasted 40 years, Each of the judges ruled for 40 years, 40 days on the mountain, 40 days of flood

  10. 70 nations, 70 languages, 70 elders, 70 souls go down to egypt,

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    I'm curious about 7 and 40 because those seem to be the most prevalent numbers for the reasons I cited, as well as those cited by Yakkov. I'm not aware of the significance of those other numbers you listed. Care to edit your answer and provide some more background on those other numbers? – Scott Mitchell May 22 '11 at 20:42
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    @ScottMitchell, see judaism.stackexchange.com/questions/tagged/mi-yodeya-series. – msh210 May 23 '11 at 1:29
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    A use for the mi.yodeya series! Hooray! – Isaac Moses May 23 '11 at 6:47

Fascinating question - especially, for me, because of the way it's cutting through to differences in paradigm of approach to text.

Just enjoying the question, I'm imagining that they are mapped onto longer time spans than more familiar natural cycle numbers - 29 or 30 days, 12 months / 365 days. Toward the end of the book of Leviticus the 7 day measure that is most familiarly the Sabbath is unrolled across years to be the sabbatical year, and across decades to be the Jubilee. The Jubilee is the 50th year - the crown of the 7th 7.

50 year intervals between Jubilees is the space of years such that every person who grows to maturity will see at least one. Some, born in a particular time, would see two. It's a measure (or a proxy), of the lifespan of a person. That's the 7 in a larger expression. The unit of 7 also has roots in consciousness. We can remember about 7 things (numbers, object names, etc.) at a time. Before electric lights, we were for sure looking at those 7 planets rolling around the sky all the time.

Those are a few ideas...on the 7 at least.


40 just means a lot much like a teenager says I have a ton of homework. It should not be taken to mean 35 + 5 = 40 This use dates back to the Sumerians. 7 is considered by many as a sacred number 12 is considered a set

it is no accident that many of our systems are organized this way

these numbers are more symbolic than sacred or magical

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    Pat, welcome to Judaism.SE and thank you for your relevant contribution. Perhaps if you could source the fact that 7 was symbolic to the Sumerians your answer would be more useful to the community. Also, we encourage registering your account so you can gain the most from the site. I look forward to seeing you around! – Double AA Feb 3 '12 at 4:18

IT seems that you were not satisfied with the answers provided. And I detect in the forum a sweet trust in God that just says, "God said it so it is then significant." I think I can connect the dots a bit for you to show you how it is that God ascribed meaning to these words. Perhaps, after I am done, a true Hebrew scholar can pick up the ball and iron out the wrinkles for you:

Related question

We see by how Adam named--words are assigned based on what they represent. He sees the creature God presents to him and he calls her woman because she came from man. He names her eve because she is the mother of all living. (The Hebrew word for Eve means life).

Seven happens to be a word we can similarly see how its significance was attached to it.

And God completed on the seventh day His work that He did, and He abstained on the seventh day from all His work that He did.
בוַיְכַל אֱלֹהִים בַּיּוֹם הַשְּׁבִיעִי מְלַאכְתּוֹ אֲשֶׁר עָשָׂה וַיִּשְׁבֹּת בַּיּוֹם הַשְּׁבִיעִי מִכָּל מְלַאכְתּוֹ אֲשֶׁר עָשָׂה:

Seven first appears on the seventh day to which it is assigned. We think of "seven" as though it is merely a number. But if we look at the linguistic connections in the context where it first appears (see the Hebrew highlighted above) we discover something. The consonants-- בֹּ and בִ are linguistically connected. If I am not mistaken, in the unpointed Hebrew text, they are identical. So while it looks in the transliteration like two different unrelated words, Shv and Shb actually show themselves in the visible text to be alike.

IT is difficult to know if the variations vocally existed in the beginning of time. Perhaps the vocal variation was assigned the very day of the event recorded in Genesis 2 in order to distinguish between what would come to be a number carrying a connotation of ceasing, and the word ceasing itself. The variations may have developed over time like dialects in regions develop and sounds of words alter slightly as people distinguished between using the word as a number and using it to actually say ceasing. Then they were employed to record the event. In any case, we have today unpointed Torah scrolls and pointed texts. One demonstrates visual similarity. The other vocal differences. I don't have access to unpointed script to demonstrate it, but if you remove the vowel pointings and the dagesh you can see the shared root: שְׁבֹּ and שְּׁבִ

In the very least, we can see how the word seven itself acquired a meaning that it continues to carry through out Torah, by virtue of being assigned to the day to which this word was assigned--a day first identified as the one on which God rested/ceased.

If we could see it in English it might be something like,
day one
day two
Day three
Day four
day five
day six
day cease

And God completed on the cease day His work that He did, and He ceased on the cease day from all His work that He did.

We see how then how also Sabbath/Shabbat-- שַׁבָּת --got its significance as a word. coming over to English I understand it:

Remember the ceasing day to keep it holy for in it God ceased from all his labor.

The seventh day received its name by its purpose God assigned it and for which He sanctified it. He blessed it because in it He rested. Thus, Seven means rest, and Shabbat, is the day on which we rest.

I have only considered the source of the significance of the word seven, and nothing about forty. Again, I am not a rabbi; I was not born a Jew; I am not a Rabbinic scholar. I took a linguistics course in college that taught me some basic common linguistic connections between v and b (and between V a U and between U and double W, W and double v etc). So, this is just the limited knowledge I brought to the text when I encountered it, and it leads me to suspect this is how they acquire their meaning.

As for all the rest of the sevens, once seven has a meaning of rest, it carries that wherever it goes, the seventh month, the seventh year, the seventh seven years, they are all respectively times of rest. One might argue it carries a connotation of a blessed rest, for those who enter into these appointed times-- "Shabbat shalom!"

As for forty, I have no insight.


The lunar calendar was in use for a long time before the bible was written. And the lunar calendar is far simpler that the solar:

  • complete cycle 28 days
  • half-moon every 14 days
  • quarter cycle, every 7 days

It's quite simply for this reason that there are seven days in a week.

And it's quite simply for this reason that the authors of Genesis used the number 7 as the number of days in which G-d created the world. When Bereishis says "seven days" (and now, this is my opinion!) it means quite literally that -- nothing to do with "eons" or "ages" and no further requirement for interpretation and mangling of the word "yaamim" to fit what we all know was not the case.

Some of the other answers given appear to "put the cart before the horse" --- and I use that expression deliberately, as another English expression "two score years and ten" springs to mind ie "70" as a life-expectancy.

In the mid to late bronze-age, 40 would have been a healthy life expectancy. Indeed, if you wanted to cleanse a population of its direct exposure to slavery, 40 years would be about right...

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    A source would greatly enhance this answer. otherwise it's simply conjecture (and somewhat simplistic, as the lunar cycle is somewhat longer than 28 days.) – Danny Schoemann Jun 10 '15 at 14:41
  • @DannySchoemann if you refer to the asker's own comment, "I'm actually more interested in natural explanations as to how these numbers became significant, not why they are significant" -- and when, naturally, any answer requires conjecture, mine are pretty good!! – user908094 Jun 15 '15 at 14:50
  • @user908094, no I'm referring to the verse that I linked to - no Rashi, and not an earlier verse. You made an assertion that in the mid-to-late bronze age 40 years was a typical life expectancy (presumably excluding infant mortality, otherwise I'm not sure what point you would be making), I was pointing out that couple of hundred years later it could be easily said that it was 70-80 years. I think that verse kind of contradicts the assertion. – Yishai Jun 15 '15 at 14:59
  • @Yishai I refer you to: uir.unisa.ac.za/bitstream/handle/10500/13257/… page 99 onwards -- but it looks like a very good & comprehensive study. – user908094 Jun 15 '15 at 15:15

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