Friend of Allah (S.W.T)

Hazrat Ibrahim (a.s): O' believer of Allah, with whose permission have you entered my house ?
Stranger: With the permission of the real owner of this house. I am the angel of death sent by Allah (swt) to inform you about the person whom Allah (swt) has selected as the "Friend of Allah" (Khalil-ullah). 

Ibrahim (a.s.): Do let me know who that saint is. I swear by Allah, which ever part of the world he lives in, I would definitely go there and meet him. Then, I would spend my whole life in his feet (serving him). 
The angel of death: You yourself are that person. 

Ibrahim (a.s): Is it true ?! Am I that person ? 
Angel of death: Yes. 

Ibrahim (a.s): Could you tell me on what basis did Allah (swt) select me as his KHALIL (friend) ? (Out of all)
Angel: Because you always keep giving everyone, but yourself never ask anyone for anything.

From that day onwards the heart of Hazrat Ibrahim (a.s.) got filled with so much fear of Allah (swt) that people near him used to hear the sound of his heart beat (similar to the sound that is created by the wings of flying birds)

[Tafsir-ibn-e-kathir volume 1, page 644]

When the angel of death informed him (a.s) that he is going to take away his life. Ibrahim (a.s) said: Ask Allah (swt), Is it possible that a friend takes away the life of a friend ? The angel went away and came back with Allah's (swt) REPLY: Is it possible that a friend dislike meeting his friend ? Ibrahim (a.s) shivered and agreed to prepare for the journey of meeting his FRIEND (ALLAH (SWT).