'Reign' in the Bible

Ish-bosheth, Saul’s son, was forty years old when he became king over Israel, and he reigned for two years. But the house of Judah followed David.

Abner said to David, “Let me stand up and go, and gather all Israel to my lord the king, so that they may make a covenant (treaty) with you, and that you may reign over all that your soul desires.” So David sent Abner away, and he went in peace.

David was thirty years old when he became king, and he reigned forty years.