“When you come to the land that G-d gives you, and possess it, and settle it, and you will say, ‘I will set a king over myself, like all the nations that are around me’” (Deut. Ch.17 v.14).
This is a mitsva incumbent on the Jewish people, that after they settle the land of Israel, they must set up a king.
What exactly is the role of a Jewish king? Furthermore, why were the Jews criticized by Samuel the prophet for asking that a king be put in place after they had settled the land (this occurred around 350 years after they had entered Israel)?
The purpose of the Jewish king is to emphasize the leadership of G-d to the Jewish people. He is to encourage them to study Torah and to keep the mitsvos. Imagine an inspirational person, able to rouse, awaken, and inspire the hearts of the Jewish people to be the best they could be. To love one another , G-d, and the Torah with their full heart. This person was the ideal of a Jewish king.
The Jewish king walks an extremely fine line. On the one hand he is a leader, and he must receive the honor and respect due a leader. On the other hand he is a leader only to inspire his subjects to follow the one true leader—G-d.
These things put the king and the Jewish people in a very difficult position: the king, because how many kings are able to walk that fine line of being a leader, but a leader only as a means for promoting the end, the acceptance of G-d as the true king.
The people were put in a difficult position for a totally different reason.
When there is an inspirational leader the ideal way to act is to emulate that person. There is also, though, the tremendous danger of allowing that person to “be in your stead”, allowing your dreams and goals to be fulfilled vicariously through that person, thus allowing yourself to slip into a mode of comfort, no longer striving to grow. When Samuel criticized the Jewish people for requesting a king this was precisely the reason. G-d did command us to appoint a king; this, however, was at the wrong time and for the wrong reason.
At that time in history, the Jewish people were on an extremely high level. The most amazing thing about this was that they did not have a national leader. This was known as the period of the Judges. The people in those generations were on an extraordinary level of righteousness. For 400 years the idea of self rule worked quite well with only two instances of wrongdoing, the concubine of Givah and the images of Micah (and even those incidents were policed by the Jews themselves, amazingly without a government to instruct them to do so).
The king must be from the family of King David. The next Jewish king will be the messiah. According to Maimonides, he will be a live human being who can unite the Jewish people under G-d. Although he has not yet come, we await him every day with longing.