Deuteronomy 17:15-18

15you shall in fact appoint a king over you whom the Lord your God chooses. One 1from among your countrymen you shall appoint as king over yourselves; you may not put a foreigner over yourselves, anyone who is not your countryman. 162In any case, he is not to acquire many horses for himself, nor shall he 3make the people return to Egypt in order to acquire many horses, since 4the Lord has said to you, ‘You shall never again return that way.’ 17And 5he shall not acquire many wives for himself, so that his heart does not turn away; nor shall he greatly increase silver and gold for himself.

18“Now it shall come about, when he sits on the throne of his kingdom, that he shall write for himself a copy of this Law on a scroll 67in the presence of the Levitical priests.