"The Oath of Pain" (痛みに誓う決意, Itami ni Chikau Ketsui) is episode 8 of the original Naruto anime.
With Kakashi captured in Zabuza's Water Prison Technique, Naruto, Sasuke, and Sakura are forced to defend against Zabuza's attacks. Kakashi tells them to run. Naruto instinctively moves to flee, but, feeling the pain in his hand, remembers his oath of pain. He decides to fight to save Kakashi and keep Tazuna alive. He tells Sasuke that he has a plan. Naruto uses his Shadow Clone Technique to completely surround Zabuza's clone, who, with one swing of his sword, causes most of Naruto's clones to scatter and disappear. The remaining Naruto passes a Fūma Shuriken to Sasuke, who senses his team-mate's plan. Sasuke uses Shadow Shuriken Technique, throwing two shurikens at Zabuza. Zabuza easily catches the first shuriken but only dodges the second at the last moment. Once past Zabuza, the second shuriken transforms back into Naruto who had disguised himself to trick the superior ninja. Naruto throws a kunai at Zabuza that forces him to stop his technique, freeing Kakashi from his prison.