'Reign Over Judah' in the Bible

And in the eighteenth year of king Jeroboam the son of Nebat began Abijam to reign over Judah.

And in the twentieth year of Jeroboam king of Israel, Asa began to reign over Judah;

And Jehoshaphat the son of Asa began to reign over Judah in the fourth year of Ahab king of Israel.