Rashi on Exodus 16:25/רש"י על שמות ט״ז:כ״ה

1ויאמר 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).