2 Samuel 5:3-5

So there at Hebron, King David made a covenant before the LORD with all the elders of Israel. And they anointed him king of Israel. David was thirty years old when he began to reign, and he reigned forty years in all. He had reigned over Judah from Hebron for seven years and six months, and from Jerusalem he reigned over all Israel and Judah for thirty-three years.