I'm not so sure that Rahim Khan is able to help his old friend Baba find redemption, but he certainly supplies the secret that helps Amir redeem himself in The Kite Runner. Amir's guilt over the betrayal of his servant/friend Hassan continues to haunt him even after Baba's death. But when Rahim Khan summons Amir to Pakistan for a visit, he provides Amir with the information that can ease his conscience. Rahim reveals Baba's greatest secret: Hassan is not Ali's son, but Baba's; Hassan is Amir's half-brother. Additionally, Hassan's son, Sohrab, is still alive and living somewhere in Afghanistan. Although Hassan is now dead, Amir knows that finding Sohrab and providing him with a safe passage through war-torn Afghanistan will make things right again. Amir accomplishes his mission, returning with the troubled Sohrab back to America where he welcomes him as part of his family: Sohrab, Amir's nephew, becomes the son that he and wife Soraya were unable to produce themselves.
Rahim had long tried to help Baba see the positive side of Amir's nature, but the stubborn Baba was not easy to convince. Rahim continued to live in Baba's house in the hope that he could one day return it to his friend, but Baba's death prevented this from happening. So, with Rahim's own death looming, he made the conscious decision to reveal Baba's secrets to the young friend he had always encouraged. Though Baba took his secret to the grave, Rahim knew that revealing Hassan's true heritage--and the knowledge about Sohrab--would create a motive to free Amir from his personal demons.
During his phone call to Amir in California, Rahim tells him to
Come. There is a way to be good again.
Another important quote occurs while Amir is taking a beating from Assef as Sohrab looks on (Chapter 22). Amir cannot stop laughing.
"WHAT'S SO FUNNY?" Assef bellowed... What was so funny was for the first time since the winter of 1975, I felt at peace... My body was broken... but I felt healed. Healed at last.