2 Samuel 5:4 in the King James Version
David was thirty years old when he began to reign, and he reigned forty years.
Context
3 So all the elders of Israel came to the king to Hebron, and King David made a covenant with them in Hebron before the LORD; and they anointed David king over Israel.
4 David was thirty years old when he began to reign, and he reigned forty years.
5 In Hebron he reigned over Judah seven years and six months, and in Jerusalem he reigned thirty-three years over all Israel and Judah.