Pirkei Avot 2:1 (excerpt):
רַבִּי אוֹמֵר... וֶהֱוֵי זָהִיר בְּמִצְוָה קַלָּה כְּבַחֲמוּרָה, שֶׁאֵין אַתָּה יוֹדֵעַ מַתַּן שְׂכָרָן שֶׁל מִצְוֹת.
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?