Or HaChaim on Exodus 16:29/אור החיים על שמות ט״ז:כ״ט

1 ראו כי ה׳ נתן לכם השבת, "See that the Lord has given you the Sabbath, etc." I have already explained that Moses felt that he did not have to spell out this commandment for the people as they had witnessed what happened and surely could draw the right conclusions therefrom. Seeing that G'd personally had revealed this commandment to them, he felt that they had absorbed it with the most potent of their senses, the sense of sight. When he said to the people: "let no one leave his place (of abode), he merely explained that the reason that G'd had not made any manna fall on that day was to save the people the bother to go and pick it up.