'Reign' in the Bible

Ish-bosheth, Saul's son, was forty years old when he began to reign over Israel, and he reigned two years. But the house of Judah followed David.

And Abner said unto David, I will arise and go, and will gather all Israel unto my lord the king, that they may make a covenant with thee, and that thou mayest reign over all that thy soul desireth. And David sent Abner away; and he went in peace.

David was thirty years old when he began to reign, and he reigned forty years.