Albert Barnes Commentary Deuteronomy 8:4

"Thy raiment waxed not old upon thee, neither did thy foot swell, these forty years." — Deuteronomy 8:4 (ASV)

They had clothes, it would seem, in abundance at the beginning of the 40 years; and during those years they had many sheep and oxen, and so must have had much material for clothing always at command. No doubt also they carried on trade in these, as in other commodities, with the Moabites and the nomadic tribes of the desert. Such ordinary supplies must not be shut out of consideration, even if they were on occasions supplemented by extraordinary providences of God, as was undoubtedly the case with their food.