2 Samuel 5:3-5

So all the elders of Israel came to the king at Hebron, and King David made a covenant with them before the LORD at Hebron; then they anointed David king over Israel. David was thirty years old when he became king, and he reigned forty years. At Hebron he reigned over Judah seven years and six months, and in Jerusalem he reigned thirty-three years over all Israel and Judah.