Deuteronomy 17:14-20 -

Israel, being under a theocracy, did not need an earthly king; but neither was this thereby precluded, provided the king chosen by the people were one whom Jehovah would approve as his vicegerent. In case, then, of their coming to desire to have a king over them like the nations around them, Moses gives instructions here as to the choice of a king, and as to the duties and obligations resting upon those who might be elevated to that office. The form in which these are conveyed clearly indicates that, at the time this was uttered, the existence of a king in Israel was contemplated as only a distant possibility.