Naruto Episode 19: The Demon in the Snow
Episode 19 of 220 of Naruto, aired February 13, 2003, 25 minutes. Available with English subtitles and dub where released.
Episode summary
Zabuza is no longer Kakashi's enemy, and thanks to a little speech by Naruto about how ninja are, Zabuza takes on Gato's men single handedly. The Demon of the Hidden Mist takes his vengeance on Gato and all of those dumb enough to follow him, and apologizes to Haku for what he did to the kind little boy. After the group takes care of the rest of Gato's men, Zabuza asks Kakashi one final request, to see Haku one final time. This is Zabuza's requiem.