Deuteronomy 17:17-20

The king must not have many wives, or his heart will be led away from God. He must not have too much silver and gold. When he becomes king, he should write a copy of the teachings on a scroll for himself, a copy taken from the priests and Levites. He should keep it with him all the time and read from it every day of his life. Then he will learn to respect the LORD his God, and he will obey all the teachings and commands. He should not think he is better than his fellow Israelites, and he must not stop obeying the law in any way so that he and his descendants may rule the kingdom for a long time.