The Consequences of Betrayal

is episode 45 of the Naruto: Shippūden anime.

Synopsis
To confuse and therefore slow down Yamato's wood clone, Kabuto modified a corpse to resemble Sai. Naruto, still recovering from the effects of his Four-Tailed state, was told to stay behind by Yamato. However, Naruto assured Yamato that he was fine, and the trio continued to follow Sai. During their pursuit, the team was forced to take a break when Sakura's own injuries took their toll on her. As she healed herself, Yamato took Naruto to one side and told him that it was he, in his Four-Tailed form, who had hurt Sakura. Naruto was shocked to discover this, and condemned his own actions, vowing to never use the fox's power again in order to not hurt those he cared for again.