Deuteronomy 17:15-19

¹⁵you shall surely set him king over you, whom Yahweh your God shall choose: one from among your brothers shall you set king over you; you may not put a foreigner over you, who is not your brother. ¹⁶Only he shall not multiply horses to himself, nor cause the people to return to Egypt, to the end that he may multiply horses; because Yahweh has said to you, You shall henceforth return no more that way. ¹⁷Neither shall he multiply wives to himself, that his heart not turn away: neither shall he greatly multiply to himself silver and gold.

¹⁸It shall be, when he sits on the throne of his kingdom, that he shall write him a copy of this law in a book, out of [that which is] before the priests the Levites: ¹⁹and it shall be with him, and he shall read therein all the days of his life; that he may learn to fear Yahweh his God, to keep all the words of this law and these statutes, to do them;