Deuteronomy 17:17KJV

15Thou shalt in any wise set king over thee, whom the LORD thy God shall choose: from among thy brethren shalt thou set king over thee: thou mayest not set a stranger over thee, which not thy brother.

16But he shall not multiply horses to himself, nor cause the people to return to Egypt, to the end that he should multiply horses: forasmuch as the LORD hath said unto you, Ye shall henceforth return no more that way.

17Neither shall he multiply wives to himself, that his heart turn not away: neither shall he greatly multiply to himself silver and gold.

18And it shall be, when he sitteth upon the throne of his kingdom, that he shall write him a copy of this law in a book out of 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 the LORD his God, to keep all the words of this law and these statutes, to do them: