forty years
1 Chronicles 3:4
These six were born unto him in Hebron; and there he reigned seven years and six months: and in Jerusalem he reigned thirty and three years.
2 Samuel 5:4
David was thirty years old when he began to reign, and he reigned forty years.
2 Samuel 5:5
In Hebron he reigned over Judah seven years and six months: and in Jerusalem he reigned thirty and three years over all Israel and Judah.
1 Kings 2:11
And the days that David reigned over Israel were forty years: seven years reigned he in Hebron, and thirty and three years reigned he in Jerusalem.