This is honestly the fall of their friendship and this causes Amirs desire for redemption in the near future, but as Amir grew up, he wanted to do good from his mistakes in his past and this is where his want for redemption came from. Amir saw how badly he was and he only wanted to be forgiven for his past actions, to Hassan and any one else that he may have done wrong to. But Amirs journey for redemption led him on a path that was long, but eventually led to the key to his own redemption, and that was sohrab. Sohrab represented Amirs past and by taking in Sohrab and being beaten by Assef, this was the key to his redemption, and ultimately shows how the fall of Amir ended up hurting many, but he tried his best to try and make everything right.