In chapter 7 of The Kite Runner, what do the sheep symbolize?

In chapter 7 of The Kite Runner, the sheep symbolizes Hassan and his sacrifice for Amir. Amir has just won the annual kite competition and Hassan has recovered the kite for him, but at the moment that Hassan retrieves the kite, he is cornered by some other boys from the neighborhood and the ringleader rapes him. Amir watches Hassan get raped and doesn't say anything and does not try to stop it. Amir allows Hassan to get raped both because he is afraid, and because he believes that "nothing was free in this world" (Hosseini, 77). After the rape, the boys allow Hassan to leave with the kite instead of taking it from him. Amir believes that "Hassan was the price I had to pay, the lamb I had to slay, to win Baba" (Hosseini, 77). Allowing Hassan to get raped ensures that Amir can get the kite he wanted, show it off at home, and hopefully win Baba's love.
While watching the rape, Amir sees a look of resignation on Hassan's face and notes that Hassan does not even fight his rapist. This makes Amir think of the celebration of Eid Al-Adha, a holiday when families traditionally butcher a sheep and divide the meat for themselves, their friends, and the poor. Amir always watches this ritual of killing the sheep and thinks that he sees a "look of acceptance" (Hosseini, 76) on the sheep's face and believes that it knows "its imminent demise is for a higher purpose" (Hosseini, 77). Just as the sheep is sacrificed to feed people on this holiday, Amir believes that Hassan's actions were a sacrifice for him.