Deuteronomy 17:18-20

18“Now when he sits on the throne of his kingdom, he is to write for himself a copy of this Torah on a scroll, from what is before the Levitical kohanim.

19It will remain with him, and he will read in it all the days of his life, in order to learn to fear Adonai his God and keep all the words of this Torah and these statutes.

20Then his heart will not be exalted above his brothers, and he will not turn from the commandment to the right or to the left—so that he may prolong his days in his kingship, he and his sons, in the midst of Israel.