Deuteronomy 17:14-20

When thou comest unto the land which Jehovah thy God giveth thee, and shalt possess it, and shalt dwell therein, and shalt say, I will set a king over me, like all the nations that are about me; thou shalt only set him king over thee whom Jehovah thy God will choose: from among thy brethren shalt thou set a king over thee; thou mayest not set a foreigner over thee, who is not thy brother. Only he shall not multiply horses to himself, nor lead back the people to Egypt, to multiply horses; for Jehovah hath said unto you, Ye shall not return again any more that way. Neither shall he multiply wives to himself, that his heart turn not away; neither shall he greatly multiply to himself silver and gold. And it shall be, when he sitteth upon the throne of his kingdom, that he shall write for himself a copy of this law in a book out of that which is before the priests, the Levites; and it shall be with him, and he shall read therein all the days of his life; that he may learn to fear Jehovah his God to keep all the words of this law and these statutes, to do them; that his heart be not lifted up above his brethren, and that he turn not aside from the commandment, to the right hand, or to the left; that he may prolong his days in his kingdom, he, and his sons, in the midst of Israel.