II Samuel 5:3-5

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