During Amir phone, call what had Rahul khan told the narrator he must do, and what were her final words to the narrator

Rahim Kahn tells Amir that "there is a way to be good again". Amir needs to go to Afghanistan to save Sohrab, Hassan's son. Amir's betrayal of Hassan so many years before still eats at Amir's soul. Going back to Afghanistan to help Hassan's son is a way for redemption.