Deuteronomy 17:16

He shall not multiply horses Though he might have horses for his own use, yet he was not to have many horses for his officers and guard, much less for war, lest he should trust in them. The multiplying horses is also forbidden, lest it should raise too great a correspondence with Egypt, which furnished Canaan with them. The Lord hath said The Lord hath now said to me, and I, by his command, declare it to you. Ye shall no more return that way Into Egypt, lest ye be again infected with her idolatries.