The Sharingan Revived: Dragon-Flame Jutsu!

is episode 30 of the original Naruto anime.

Synopsis
Sasuke and the Kusa ninja engage in combat. After a long, difficult battle, Sasuke seemingly ends the battle with a blast of fire to the ninja's face. However, the ninja awakens with his face partially melted off, revealing another face underneath. The ninja reveals himself to be Orochimaru and then extending his neck, he bites Sasuke and leaves behind a cursed seal, wishes Sasuke luck in surviving, and leaves. Anko finds Orochimaru and attacks him, intent on killing her former sensei for his crimes, even at the potential cost of her own life; unfortunately she fails, and Orochimaru escapes.