Naruto Episode 15
Naruto and Sasuke both attempt to destroy the ice mirrors, though both are unsuccessful, leading Kakashi to believe that Haku has a kekkei genkai. He once again reveals his Sharingan. Zabuza reveals that he is able to counter the Sharingan through hiding himself in mist, and he lands a strike on Kakashi.
Source: Wikipedia
Naruto Episode 15 – Zero Visibility: The Sharingan Shatters
