John Gill Commentary Numbers 11:9

"And when the dew fell upon the camp in the night, the manna fell upon it." — Numbers 11:9 (ASV)

And when the dew fell upon the camp in the night
As it usually, and even constantly did:

the manna fell upon it ;
as constantly, and had thereby a clean place to fall on; and then another dew fell upon that, which kept it the cleaner still, and from any vermin creeping upon it; see (Exodus 16:14) ; so careful was the Lord of this their provision, and so constantly every morning were they supplied with it: and which fell in the night when they were asleep, and at rest, and without any labour of theirs; and was ready to their hands when they arose, and had nothing to do but gather it; and yet were so ungrateful as to make light of it, and despise it.