Exodus 16:4

16:4 Then the Lord said to Moses, “I am going to rain bread from heaven for you, and the people will go out and gather the amount for each day, so that I may test them. Will they will walk in my law or not?

Exodus 16:14-15

16:14 When the layer of dew had evaporated, there on the surface of the desert was a thin flaky substance, thin like frost on the earth. 16:15 When the Israelites saw it, they said to one another, “What is it?” because they did not know what it was. Moses said to them, “It is the bread that the Lord has given you for food.