Deuteronomy 8:1-3

Be careful to follow every command I am giving you today, so that you may live and increase and may enter and possess the land that the LORD promised on oath to your forefathers. Remember how the LORD your God led you all the way in the desert these forty years, to humble you and to test you in order to know what was in your heart, whether or not you would keep his commands. He humbled you, causing you to hunger and then feeding you with manna, which neither you nor your fathers had known, to teach you that man does not live on bread alone but on every word that comes from the mouth of the LORD.