What does R. Yehudah mean in Avot 2:1 when he states that we do not know the reward of mitzvot?

Question

Pirkei Avot 2:1 (excerpt):

רַבִּי אוֹמֵר... וֶהֱוֵי זָהִיר בְּמִצְוָה קַלָּה כְּבַחֲמוּרָה, שֶׁאֵין אַתָּה יוֹדֵעַ מַתַּן שְׂכָרָן שֶׁל מִצְוֹת.

My translation:

Rabbi [Yehuda haNasi] said: ... And be as careful with a light commandment as with a weighty one, for you do not know the reward given for mitzvot.

Actually, we do know the reward for mitzvoth, in a general sense. Two examples:

• Devarim (Deut.() 7:12-16 mentions items like blessing the fruits of the land and your belly (children; removing sicknesses, being blessed above all other nations, etc.
• Devarim (Deut.) 28:1-13 mentions some of the same ideas as above and adds being blessed when leaving and coming, other nations fearing us, etc.

We also have a few cases where the reward for specific commandments are mentioned. In particular, the reward of long life is mentioned regarding:

• Honoring parents (E.g. - Shmot (Ex.) 20:12)
• Shilu'ach Hakan - chasing a way the mother bird and taking the chicks or eggs (Devarim (Deut.) 22:6)

If Rav Yehuda is talking about the reward of one mitzvah relative to another one, it seems strange that he uses the terms "light" and "weighty". In the phrasing, he assumes that we know what they are. If he were attempting to explain these terms, perhaps he should have said something like,

"Don't assume that one mitzvah is lighter than another based on its reward system, because you don't know what the reward for each mitzvah is."

It doesn't seem to me that he is trying to explain these terms, here.

Based on this, what does Rav Yehuda mean by stating that we don't know what the reward for mitzvot are?

Answer 1

Tos'fos Yom Tov explains that although the type of reward for mitzvos is specified to some extent (and he cites some of the same verses you do), the quantity of that reward depends on the effort we put in to the mitzva performance and is impossible for us to determine.

Answer 2

Since this question is being asked as we approach Shabbat Kodesh, m'varchim Chodesh Shvat for 5776, it seems appropriate to answer this with the following link.

http://www.hebrewbooks.org/pdfpager.aspx?req=16001&hilite=2c8223d8-ae0e-40ec-9a4e-82e404d247a4&st=יודע+מתן+שכרן&pgnum=146

This is a talk that the Lubavitcher Rebbe gave for Shabbat Kodesh, m'varchim Menachem Av in 1987.

He explains that there are two aspects to the mitzvot, one that relates to the finite and measurement, as in light and heavy commandments, and one that relates to the infinite, meaning how all the commandments are G-d's will. This second aspect is in the realm of 'unknowable', meaning it transcends knowledge.

He goes on to say that what "Rebbe" (Yehuda HaNasi) is saying is that we are to 'illuminate' all mitzvot with both the finite element that we relate to as finite, created beings and that infinite quality.

Answer 3

Biurim LePirkei Avos says that the reward for the finite aspect of the mitsva is finite and therefore knowable. But in the other hand the reward for the infinite aspect of mitsva is infinite and therefore unknowable.