Pure Terror! The House of Orochimaru!

is episode 139 of the original Naruto anime.

Synopsis
Sasame leads Naruto, Jiraiya, and Sakura to Orochimaru's hideout. They send Sasame back to the village because of the danger level. Jiraiya summons Gamakichi to go in first and investigate. The four come to three tunnels. Jiraiya goes off to the right, Naruto and Sakura down the middle and Gamakichi down the left. As Sakura enters a large vacant room, she encounters Kabuto and Orochimaru, who already have the upper hand.