Deuteronomy 17:14-18

“When you enter the land which the Lord your God is giving you, and you take possession of it and live in it, and you say, ‘I will appoint a king over me like all the nations who are around me,’

you shall in fact appoint a king over you whom the Lord your God chooses. One from among your countrymen you shall appoint as king over yourselves; you may not put a foreigner over yourselves, anyone who is not your countryman.

In any case, he is not to acquire many horses for himself, nor shall he make the people return to Egypt in order to acquire many horses, since the Lord has said to you, ‘You shall never again return that way.’

And he 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.

“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 in the presence of the Levitical priests.