The Oath of Pain

is episode 8 of the original Naruto anime.

Synopsis
With Kakashi captured in Zabuza's Water Prison Technique, Naruto, Sasuke, and Sakura must defend against Zabuza's attacks. Kakashi tells them to run, and Naruto becomes scared and wants to flee, but he soon remembers his oath of pain. He has no other choice but to fight, so they can save Kakashi and keep Tazuna alive. Realizes that he must work together with Sasuke to save Kakashi, Naruto uses his Shadow Clone Technique, so all the clones all jump and completely surround Zabuza's clone. Then Zabuza's clone swings his sword and most of the clones scatter and disappear. The last of the Naruto clones takes a windmill shuriken (that Naruto transformed into) and gives it to Sasuke. Then Sasuke does Shadow Shuriken Technique, the first shuriken was Sasuke's own shuriken and the second one was Naruto's. Naruto's shuriken was hidden under Sasuke's. Zabuza catches Sasuke's shuriken and dodges Naruto's. Naruto then transforms back in to his original form and throws a kunai at Zabuza, forcing him to stop his jutsu, freeing Kakashi.