Zabuza's Blade

is episode 115 of the Naruto: Shippūden anime.

Synopsis
Sasuke frees Suigetsu from his hydro capsule and requests his services. Suigetsu responds that he would gladly give them, on condition that he helps him find Zabuza's sword. They fail to find the blade at his grave, but learn that it is in the possession of a man named Tenzen Daikoku. Sasuke uses Tenzen's guarded fortress to test Suigetsu's combat abilities, and Suigetsu gets the blade without much effort. As promised, Suigetsu joins up with Sasuke, and goes with him to the Southern hideout.