"What promise does Amir breaks"

Amir breaks his promise about taking sohrab to America without being harmed. He was sad and hurt that he broke the promise he made to Sohrab because he made a big promise and broke, and to try and make up for it he volunteered and prayed on doin certain things that have to do with religion like fasting for example. I also think that Amir broke a promise by saying that Sohrab can be part of the family.