Deuteronomy 17:14-17

14 When you are come to the land which Yahweh your God gives you, and shall possess it, and shall dwell therein, and shall say, I will set a king over me, like all the nations that are round about me; 15 you 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. 16 Only 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. 17 Neither shall he multiply wives to himself, that his heart not turn away: neither shall he greatly multiply to himself silver and gold.