Siman 298

(8.) He said to someone: "The power that King David, upon him be peace, had to say 'Absalom my son, my son' eight times — and through this he elevated him from the seven chambers of gehinom and brought him into Gan Eden, as our Rabbis of blessed memory said — this power he also has. That through his words alone he can also elevate a person from all the seven chambers of gehinom and bring him into Gan Eden."