Kommentar zu Schemot 16:25

ויאמר משה אכלהו היום AND MOSES SAID, EAT THAT THIS DAY etc. — In the morning, when they had been accustomed to go forth and gather it, they came to enquire, “Shall we go out or not?” He replied to them, “What you have in your possession eat (אכלהו היום)”. In the evening they again came before him and asked him, “How is it now about going out?” He answered them, שבת היום “Today is the Sabbath”. He saw that they were worried believing perhaps the Manna had stopped and would not again fall; he therefore said to them, “Today ye shall not find it [in the field]”. What reason was there to say “Today”? — Today you will not find it, but tomorrow you will find it (Mekhilta d'Rabbi Yishmael 16:7).

אכלוהו היום, at fixed times, from this date onward.

אכלהו היום כי שבת היום, "eat it to-day for to-day is a Sabbath, etc." Why did Moses have to command the people to eat the manna? Perhaps this was because he had previously told them to leave aside what was left to keep it till the following morning. He had not spelled out to them that they not only could keep it but were also allowed to eat it. Although we do not have Moses on record as having forbidden the consumption of any left-over manna on other days, it seems evident from the verses about the way to treat the manna on the Sabbath that he must have forbidden the left-overs. Perhaps the prohibition of such left-overs stems from the same consideration as the prohibition to consume meat from sacrificial offerings after the time limit allocated to such a sacrifice has expired. Compare Chulin 114 where our sages state that "anything which I have declared as rejected by Me, you must not eat." Moses' emphasis on "eat it to-day," clearly indicates that it was not to be eaten after to-day. Moses added the words "for to-day is a Sabbath," in order that the Israelites should not form the impression that the prohibition to eat yesterday's manna on the morrow also applied to the Sabbath.