Deuteronomy 17:15-17

you may indeed set a king over you whom the LORD your God will choose. One from among your brothers you shall set as king over you. You may not put a foreigner over you, who is not your brother. Only he must not acquire many horses for himself or cause the people to return to Egypt in order to acquire many horses, since the LORD has said to you, ‘You shall never return that way again.’ And he shall not acquire many wives for himself, lest his heart turn away, nor shall he acquire for himself excessive silver and gold.