Deuteronomy 17:18-19

18And 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;

19and it shall be with him, and he shall read therein all the days of his life; that he may learn to fear Jehovah his 1God, to keep all the words of this law and these statutes, to do them;