In his phone conversation, Rahim Khan says to Amir,
"Come. There is a way to be good again".
This quote is significant because it indicates that Rahim Khan has known Amir's secret all these years, the secret of Amir's cowardice when Hassan was being attacked by bullies while running a kite for Amir (Chapter 14).
When Amir visits Rahim Khan, he thinks,
"'...the elephant in the room'...Nothing could more correctly describe the initial moments of my reunion with Rahim Khan".
Amir's reunion with Rahim Khan is uncomfortable because of what is left unsaid. Rahim Khan knows Amir's secret shame, but does not mention it. Amir also notes,
"Rahim Khan had always been one of the most instinctive people I'd ever met".
When Amir had been a child, Rahim Khan had been the only one who had picked up on Amir's hurt at his father's treatment of him. Rahim Khan also knows that something terrible had happened between Amir and Hassan, and that the memory of the incident haunts Amir to this day (Chapter 15).
Amir asks Rahim Khan how conditions are in Afghanistan under the Taliban, and the old man replies succinctly,
"They don't let you be human".
In six short words, he describes the severity of the Taliban's oppression of the people (Chapter 15).
Rahim Khan remembers Hassan's words when he agreed to come live at Baba's house with Rahim Khan. Hassan said,
"Agha sahib was like my second father...God give him peace".
Hassan's words are ironic, because even though he is not aware of the fact, Baba was indeed his biological father (Chapter 16).
In looking at the photo of Hassan, Amir notes,
"...it was in the way he smiled. Looking at the photo, one might have concluded that this was a man who thought the world had been good to him".
This quote captures the essence of Hassan's character. Even though he had always been treated as an inferior because of his ethnicity, Hassan never complained or expressed unhappiness at his lot in life. His attitude was always positive and loving, and he had the amazing ability to appreciate the good things he was given, and to overlook the bad (Chapter 17).