Musar על אבות 3:7

לקטו ממנו איש לפי אכלו. The Torah tells us here how much a person needs to eat to sustain himself. This is the reason the measurements are spelled out in such detail, as well as the fact that people's subjective estimate of their "needs" were proven wrong, since, regardless of how much they believed they had gathered, once they measured it, they found that every person had obtained the same quantity. When the Torah afterwards describes some people as "storing" extra מן for the following day against Moses' instructions, and it turned into worms, this was a warning of what our sages (Avot 2,7) called מרבה בשר מרבה רמה, that he who eats excessively, over and beyond his needs, only increases the number of worms that will eventually invade his corpse. When the Torah added: ויבאש, this is a hint that decomposition can set in even during one's lifetime when one gorges oneself on too much unneeded food. I have enlarged on this subject in my treatise שער האותיות under the heading of שלחן and the letter ק for קדושה.