Beyond the Limit of Darkness and Light

is episode 79 of the original Naruto anime.

Synopsis
As they transformed, and while Gamabunta held Shukaku in place, Naruto awakened Gaara. Naruto delivered a headbutt to Gaara, destroying Shukaku's form. Across Konoha, Konoha's ninja, including the parents of many of the Genin, began the counterattack on the invading forces. At the site of the Third Hokage's battle with Orochimaru, the Third realized that he didn't have enough strength left to fully seal Orochimaru's soul, and instead opted to seal his former pupil's arms. He successfully did so, thus robbing Orochimaru of his ability to use jutsu. Wishing his student a fond farewell, the Third died after reciting one last proverb. At this time Naruto and Gaara leapt at each other, and Naruto succeeded in delivering the winning blow.