Albert Barnes Commentary 2 Kings 13:1

"In the three and twentieth year of Joash the son of Ahaziah, king of Judah, Jehoahaz the son of Jehu began to reign over Israel in Samaria, [and reigned] seventeen years." — 2 Kings 13:1 (ASV)

In this chapter, the history of the kingdom of Israel is traced through the two reigns of Jehoahaz and Jehoash. The history of Judah is resumed in 2 Kings 14:0.

In the twenty-third year—Rather, the “twenty-first year.” See 2 Kings 13:10.