Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 173
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 173, with English translation by Maimonides (Rambam).
למנות מלך, שנאמר: "שום תשים עליך מלך" (דברים יז,טו).
To appoint a king, as [Deuteronomy 17:15] states: "You shall surely set a king upon yourselves."