Deuteronomy 17:16-20

16However, he must not acquire many horses for himself or send the people back to Egypt to acquire many horses, for the Lord has told you, ‘You are never to go back that way again.’

17He must not acquire many wives for himself so that his heart won’t go astray. He must not acquire very large amounts of silver and gold for himself.

18When he is seated on his royal throne, he is to write a copy of this instruction for himself on a scroll in the presence of the Levitical priests.

19It is to remain with him, and he is to read from it all the days of his life, so that he may learn to fear the Lord his God, to observe all the words of this instruction, and to do these statutes.

20Then his heart will not be exalted above his countrymen, he will not turn from this command to the right or the left, and he and his sons will continue reigning many years in Israel.