Exodus 16:4, 13-15

Then the LORD said to Moses, “Behold, I will cause bread to rain from heaven for you; the people shall go out and gather a day’s portion every day, so that I may test them [to determine] whether or not they will walk [obediently] in My instruction (law).

So in the evening the quails came up and covered the camp, and in the morning there was a blanket of dew around the camp. When the layer of dew evaporated, on the surface of the wilderness there was a fine, flake-like thing, as fine as frost on the ground. When the Israelites saw it, they said to one another, “What is it?” For they did not know what it was. And Moses said to them, “This is the bread which the LORD has given you to eat. [John 6:31, 33]