Deuteronomy 8:2-3

Remember the long way that the LORD your God has led you these forty years in the wilderness, in order to humble you, testing you to know what was in your heart, whether or not you would keep his commandments. He humbled you by letting you hunger, then by feeding you with manna, with which neither you nor your ancestors were acquainted, in order to make you understand that one does not live by bread alone, but by every word that comes from the mouth of the LORD.