Exodus 16:35

Did eat manna forty years - This does not necessarily imply that the Israelites were fed exclusively on manna, or that the supply was continuous during forty years: but that whenever it might be needed, owing to the total or partial failure of other food, it was given until they entered the promised land. They had numerous flocks and herds, which were not slaughtered (see Numbers 11:22), but which gave them milk, cheese and of course a limited supply of flesh: nor is there any reason to suppose that during a considerable part of that time they may not have cultivated some spots of fertile ground in the wilderness. We may assume, as in most cases of miracle, that the supernatural supply was commensurate with their actual necessity. The manna was not withheld in fact until the Israelites had passed the Jordan.