2 Samuel 5:3-5

So all the elders of Israel came to the king at Hebron. King David made a covenant with them at Hebron in the LORD’s presence, and they anointed David king over Israel. David was 30 years old when he began his reign; he reigned 40 years. In Hebron he reigned over Judah seven years and six months, and in Jerusalem he reigned 33 years over all Israel and Judah.