Naruto Episode 7
After the attack, Tazuna admits that the mission is much more dangerous than originally intended, but after Team 7 hears of Tazuna’s desire to build a bridge to save the impoverished Land of Waves from the criminal Gato, they agree to go through with the mission regardless. The group is soon stopped by Zabuza Momochi, an opponent dangerous enough for Kakashi to reveal his Sharingan eye.
Source: Wikipedia
Naruto Episode 7 – The Assassin of the Mist!
