Albert Barnes Commentary Acts 13:21

"And afterward they asked for a king: and God gave unto them Saul the son of Kish, a man of the tribe of Benjamin, for the space of forty years." — Acts 13:21 (ASV)

And afterward they desired a king. See 1 Samuel 8:5; Hosea 13:10. It was predicted that they would have a king, Deuteronomy 17:14–15.

Saul the son of Cis. Cis is the Greek way of writing the Hebrew name Kish. In the Old Testament it is uniformly written Kish; and it is regrettable that this has not been retained in the New Testament. See 1 Samuel 9:1.

By the space of forty years. During forty years. The Old Testament has not mentioned the time during which Saul reigned. Josephus says (Antiquities, Book 6, Chapter 14, section 9) that he reigned eighteen years while Samuel was alive, and twenty-two years after his death. But Dr. Doddridge (Note on this passage) has shown that this cannot be correct, and that he probably reigned, as some copies of Josephus have it, only two years after the death of Samuel. Many critics suppose that the term of forty years mentioned here also includes the time in which Samuel judged the people. This supposition does not violate the text in this passage and is plausible. See Doddridge and Grotius on this passage.