For the kings of Israel and Judah, Scripture usually records their age when they became king and how long they ruled (for example, 2 Samuel 5:4–5; 1 Kings 14:21).
thirty years old: This age is likely when Saul became king. The Hebrew text and most Greek manuscripts leave out the number, making the original wording unclear.
reigned over Israel forty-two years: See the textual note in the Berean Standard Bible. The Masoretic Text reads "over Israel two years." Most scholars think something is missing from the original manuscript, probably due to a copying mistake. Most English translations use forty-two based on the approximate number in Acts 13:21.