Deuteronomy 8:2-5

And you shall remember [always] all the ways which the LORD your God has led you these forty years in the wilderness, so that He might humble you and test you, to know what was in your heart (mind), whether you would keep His commandments or not. He humbled you and allowed you to be hungry and fed you with manna, [a substance] which you did not know, nor did your fathers know, so that He might make you understand [by personal experience] that man does not live by bread alone, but man lives by every word that proceeds out of the mouth of the LORD. Your clothing did not wear out on you, nor did your feet swell these forty years. Therefore, know in your heart (be fully cognizant) that the LORD your God disciplines and instructs you just as a man disciplines and instructs his son.