Deuteronomy 17:15-17

If this happens, be sure to select as king the man the LORD your God chooses. You must appoint a fellow Israelite; he may not be a foreigner. “The king must not build up a large stable of horses for himself or send his people to Egypt to buy horses, for the LORD has told you, ‘You must never return to Egypt.’ The king must not take many wives for himself, because they will turn his heart away from the LORD. And he must not accumulate large amounts of wealth in silver and gold for himself.