Deuteronomy 8:1-5

ALL THE commandments which I command you this day you shall be watchful to do, that you may live and multiply and go in and possess the land which the Lord swore to give to your fathers. And you shall [earnestly] remember all the way which the Lord your God led you these forty years in the wilderness, to humble you and to prove you, to know what was in your [mind and] heart, whether you would keep His commandments or not. And He humbled you and allowed you to hunger and fed you with manna, which you did not know nor did your fathers know, that He might make you recognize and personally know that man does not live by bread only, but man lives by every word that proceeds out of the mouth of the Lord. Your clothing did not become old upon you nor did your feet swell these forty years. Know also in your [minds and] hearts that, as a man disciplines and instructs his son, so the Lord your God disciplines and instructs you.