Deuteronomy 17:15-18

15If that happens, you must only accept a king that the Lord your God chooses. Choose a king from among your own people. Do not choose anyone who is not an Israelite.

16A king must not get a lot of horses for himself. He must not send his people back to Egypt to buy more horses. The Lord has said to you, ‘Never return to Egypt for any reason!’

17A king must not marry many wives. They may turn his thoughts away from the Lord. He must not store a lot of silver and gold for himself.

18When anyone starts to rule as king, he must copy this Law of God on a scroll. The scroll will be a copy of the one that belongs to the Levite priests.