Answer:
From the book The Kite Runner by Khaled Hosseini, Amir has a fleeting thought during his wedding of how he betrayed Hassan when he decided not to help him just to prove to his father that he captured the kite in the competition. He also betrayed Hassan when he doesn't defend him from Assef who was sexually assaulting him.
The significance of this is that it shows that Amir had matured and grown in his strength of character and compassion.
