Hebrew beginner, here. I was asking why the prefix for "not" was usually לא but occasionally אל. Some kind Hebrew students told me אל was only used for future tense, saying not to do something.

One example is in Proverbs 4:6 -


Could that be written like this?


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    Welcome to Mi Yodeya, and thanks for bringing your question here! I hope you have continued success in your studies, and I hope that Mi Yodeya continues to be helpful with your Judaism-based Hebrew questions. Check out what else we've got under grammar-dikduk. I recommend that you support this proposal for a more general Hebrew-language StackExchange site. Finally, please edit your profile and give yourself a name!
    – Isaac Moses
    Commented Dec 20, 2013 at 4:26
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    While these words appear in s good number of Jewish texts, this is primarily a grammar question, not a Judaism question. That said, welcome to the site, and I hope you stick around.
    – Seth J
    Commented Dec 20, 2013 at 4:51
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    @Isaac, well, kinda, but that would make every Hebrew grammar question on topic.
    – Seth J
    Commented Dec 20, 2013 at 14:02
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    @SethJ, only to the extent that they are about Biblical Hebrew and indicate a motivation of understanding part or all of Tanach. On the opposite extreme, do you really think that the questions in all of the grammar and word-meaning Rashis, e.g., should be off-topic here? Given the tight integration of language analysis into Torah study and the fact that learning Hebrew is actually considered a Mitzva by the Rambam, I think we ought to have a pretty inclusive attitude to Hebrew questions that are demonstrably Judaism-motivated.
    – Isaac Moses
    Commented Dec 20, 2013 at 16:25
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3 Answers 3


The Meshech Chochmah has a novel approach to these two words. He writes that אל has more of a tone of a request (although still obligatory). That's why נא, please, only ever accompanies אל (such as Genesis 18:3), and never לא, which is more of a more forceful command.

He proceeds to give several cases in Chumash where this proves to be true. Rav Kupperman, in his notes to Meshech Chochmah, points out that these examples show three types of cases where the Torah will choose אל instead of לא:

  1. When the desire of the Torah is to command something, but for one reason or another Hashem didn't want to make it a full-forced command. He sees this from Leviticus 25:36, which sounds like it's prohibiting lending to a ger toshav with interest (which it isn't, as it's only assur miderabannan, see Bava Metziah 70b. He's saying Chazal saw the need to prohibit from this pasuk which uses אל).

  2. When the prohibition is so self-evident it doesn't need to be written in a strong form, like Leviticus 25:14, the prohibition to overcharge another (he says from societal sense it's a bad idea).

  3. Sometimes it's simply not feasible to have a mitzvah stated in the form of a definite command. An example is Leviticus 19:4, which makes a prohibition on a person's thoughts, which are hard to control.

  • @MonicaCellio maybe this is the source to what you were taught
    – robev
    Commented Jan 18, 2018 at 3:11
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    I just saw this over Shabbos and came to this thread to post this Meshech Chochma! I found his comments about ribbis particularly interesting. +1! Commented Jan 22, 2018 at 19:19

In Biblical Hebrew, לא can be used instead of אל, as in "לא תרצח". The opposite is not true; "אל" cannot replace "לא" in most cases.

In modern Hebrew, you would usually want to stick with אל in order to forbid doing something, and לא in all other cases.

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    I was taught (for biblical Hebrew) to think of לא as "don't" and אל as "thou shalt not" -- both mean "don't do that", but the latter is more emphatic and perhaps more durative. But I don't have a source. Commented Dec 25, 2013 at 14:52
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    Nice observation, Monica, but probably the other way round; in Biblical Hebrew לא would tend to be more durative and used for eternal laws (as in the ten commandments) while אל will usually be used for immediate action ("היו נכונים לשלושת ימים, אל תגשו אל אשה)
    – Sambusak
    Commented Dec 26, 2013 at 9:53
  • Oops, you're right -- thanks for the correction! Commented Dec 26, 2013 at 14:07

Rashbam agrees with the "kind Hebrew students" who told you that "al" refers to the future.

Genesis 49:6

בסודם אל תבא נפשי – יהי רצון שלא תבא נפשי בעצתם כי כל אל שבתורה להבא הן או קללה או בקשה או ציווי לא יימצא אל לשעבר לכן אין לפרש לא באה נפשי

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