In "The Kite Runner," why do you think Amir recalls this memory when he witnesses Hassan's tragedy in the alleyway?
It is this central guilt that also keeps Amir from healing his relationship with his father, his roots, and himself. He idolized his father with the eyes of a child. His father tells him that the worst thing to do is to lie. Amir feels that his father has been an honest man, unwilling to compromise even in the face of death as illustrated in the confrontation with the Soviet soldiers on their journey out of Afghanistan. However, he keeps this secret, and later on realizes that he has been a coward not only to a friend, but to a brother, and in essence has betrayed his father by betraying his father's son. It is necessary as a literary vehicle, because it becomes the impetus and driving force for his return to Afghanistan and his quest to bring home his nephew, Hassan's son. Amir holds fast to the guilt and this act of cowardice in his past in order to anchor him to his commitment of the rescue of the child from the same blue-eyed villain who assaulted his brother, Hassan.
The memory that Amir flashes to while Hassan is being assaulted is that of an Afghan celebration the entails the sacrifice of a sheep. During one particular celebration, Amir had locked eyes with the sheep at the moment of its death, and felt that the sheep understood there was a purpose to his death, and gives is understanding.
Amir could be focusing on this memory because just as the time he watched the sheep's death and stood by and did nothing, he is again standing by as a witness without action. Amir's own conscience is trying to rationalize that Hassan would understand that it would be pointless to put himself in danger as well, and willingly sacrifices himself for the greater good-further violence.