Deuteronomy 8:2-6

You shall remember all the way which the LORD your God has led you in the wilderness these forty years, that He might humble you, testing you, to know what was in your heart, whether you would keep His commandments or not. He humbled you and let you be hungry, and fed you with manna which you did not know, nor did your fathers know, that He might make you understand that man does not live by bread alone, but man lives by everything that proceeds out of the mouth of the LORD. Your clothing did not wear out on you, nor did your foot swell these forty years. Thus you are to know in your heart that the LORD your God was disciplining you just as a man disciplines his son. Therefore, you shall keep the commandments of the LORD your God, to walk in His ways and to fear Him.