When Amir goes back to Kabul, and finds that Assef is now a Taliban member, and has 'bought' and abused Sohrab, he now knows what he must do to end his atonement. By finishing the fight with Assef that was started years ago in Amir's childhood, but stopped by Hassan, he can finally get the physical punishment he feels he deserves, and the redemption he craves. There is also a strong sense of fate and destiny in this, as Assef promised that he would get the boys back for the unfinished fight (which he has done already with Hassan). The quote 'Now it was my turn.' emphasises this idea of destiny, it is a short simple sentence which shows that Amir knows that this is his fate, and gives it a sense of finality. The possesive determiner 'my' suggests that Amir has realized that fighting Assef is something he has to do alone, in order to finish his redemption process. This could also be why he has not told Soraya about what he is doing; his final redemption must be totally independent.
Assef himself also realises the significance of the fight that is about to happen. This is shown where he instructs the guards not to come into the room, saying that Amir and himself have to 'finish an old bit of business'. His euphemism here seems to be mocking Amir which suggests that he knows the impact that this fight will have on Amir and his redemption process. The plosive alliteration is 'bit of business' also suggests this, as well as Assef's power over Amir and his potential atonement.
During the fight, Amir reflects back on his childhood memories of Hassan; the physical pain he is feeling mirrors the mental pain he has gone through since the rape. Hosseini writes 'I don't know at what point I started laughing, but I did.' The non-finite verb 'laughing' is repeated throughout this paragraph, showing that by being harmed by Assef has provided him with release from the mental pain; he is laughing with relief. Amir says that 'for the first time since the winter of 1975, i felt at peace' implying that he nows feels that his redemption is complete; he has found tranquility in the fight.
However, it soon becomes clear that Amir's redemption is not over, he has to endure more obstacles to complete the cycle. Throughout the next chapters, we see the struggle to bring Sohrab back to America, ending in Sohrab attempting suicide, and becoming vacant and withdrawn. This is significant because the carefully built up trust between Sohrab and Amir being destroyed parallels the trust between Hassan and Amir being destroyed when Amir plants the watch under the mattress. However, at the very end of the novel Amir and Sohrab go kite flying together, and we see Sohrab smile for the first time since his suicide attempt. Hosseini's short, minor sentence 'A smile.' conveys the importance of this smile; a breakthrough in Amir and Sohrab's ruined relationship and trust. It also mirrors the way that Hassan learned to smile again after the traumatic experience that he himself went through. With this smile, Amir knows that his life has been transformed, he has rid himself of his guilt and achieved redemption. His redemption does not come from fighting with Assef, or bringing Sohrab to America, as he expected it would, but from Amir finally forgiving himself for what he did. The kite flying is very important here, not only because of it's connections with Hassan, but because it symbolises the hope and freedom that Amir now has. This is represented by Hosseini's use of short, fragmented sentences on the very last page of the book, such as 'But I'll take it. With open arms.' which conveys this idea of Amir's new found hope for Sohrab's future.
Like Amir, other characters in the novel also have past sins that they feel they need redemption for, like Baba. His redemption lies in taking Amir to America, and working at a garage to provide for the two of them, even though he (Baba) would have been happier in Peshawar. This is shown where Baba says 'Peshawar was good for me. Not for you.' which shows that he is finally trying to redeem himself for his past unequal treatment of Hassan and Amir, his sons, by becoming a better father to Amir; aknowledging his needs and paying him the attention that he was denied as a child. We also see Amir being described as 'my son' frequently in Baba's speech after the move to America, for example 'Tonight, I drinking with my son'. The possessive determiner 'my' shows that Baba has now accepted Amir fully, and treats him as an equal, as opposed to during their time in Kabul, where Amir mostly felt neglected by Baba.
The similarities between Baba and Amir are also highlighted here; both of their redemption journeys are both physical and mental. For Amir, it is going back to Kabul, and for Baba it is the move to America.
Sohrab is also presented as feeling as if he needs redemption, after he shoots Assef in the eye with the slingshot. Because he has been brought up to be very religious, he seeks redemption by going to the Shah Faisal mosque. Unlike the other characters, he is open to Amir about his guilt and fears. He says "Will God put me in hell for what I did to that man?", showing that he needs reassurance about his redemption, and also that he has inherited Hassan's sense of morals. Sohrab then goes on to say "Do you think father is disappointed in me?" showing that his father is equally as important to him as the idea of going to hell for what he did. Amir gives Sohrab reassurance, and a new chance in life, when he offers Sohrab the option of goign back to America with him. He does this at the mosque, with 'the bright lights of the house of God shining on us' which shows Sohrab's close link with his religion, and foreshadows Amir later in the novel, when he becomes more religious.
In conclusion, the idea of redemption is portrayed as a universal theme, something which cannot be obtained until forgiveness is reached; not from God, but from yourself.