Deuteronomy 8:2-3

Remember that the LORD your God led you on the entire journey these forty years in the wilderness, so that he might humble you and test you to know what was in your heart, whether or not you would keep his commands. He humbled you by letting you go hungry; then he gave you manna to eat, which you and your ancestors had not known, so that you might learn that man does not live on bread alone but on every word that comes from the mouth of the LORD.