2 Samuel 5:3-5

3So all the elders (tribal leaders) of Israel came to the king at Hebron, and King David made a covenant with them at Hebron before the Lord; and they anointed him king over Israel.

4David was thirty years old when he became king, and he reigned forty years.

5In Hebron he reigned over Judah seven years and six months, and in Jerusalem he reigned thirty-three years over all Israel and Judah.