Or HaChaim on Exodus 16:19/אור החיים על שמות ט״ז:י״ט

1 ויאמר משה…אל יותר ממנו עד בקר, Moses said…not to leave over from it till the following morning. It is possible that Moses issued this directive on his own. He did so because he knew that G'd would provide daily rations. He interpreted G'd's intention as being that one day's food supply should not serve as preparation for the following day's needs. This may be why the Torah phrases Israel's disobedience as "they did not listen to Moses," instead of simply saying: "they left some over till the morning."

2Furthermore, why was it not sufficient to say: "they did not listen and left some over?" This would have told us that they did not listen to the one who had given the instructions. According to our interpretation the meaning of "and they did not listen" means the reason they ignored Moses' instructions was that they were clever enough to perceive that the instructions originated with Moses and not with G'd. This also explains the fact that Moses had introduced the instructions he gave concerning collecting the manna in verse 16 as being in the name of G'd. He had not done so previously. If the manna turned bad and sprouted worms this shows that G'd agreed with Moses' intiative.

3It is also possible that every instruction Moses issued originated with G'd; seeing Moses had already introduced his directives concerning collection of the manna as instructions given to him by G'd, he did not see the need to re-emphasize this at every juncture. The Israelites misunderstood this, thinking Moses had acted on his own. They also did not know that instructions issued by a prophet are to be obeyed even if the prophet did not receive specific instructions concerning them from G'd.