Bukhari Collection: ::Book Number 5:: Hadith # 13
Narrated Abu Ad-Darda:While I was sitting with the Prophet, Abu Bakr came, lifting up one corner of h is garment uncovering h is knee. The Prophet said, "Your companion has had a quarrel." Abu Bakr greeted (the Prophet ) and said, "O Allah's Apostle! There was something (i.e. quarrel) between me and the Son of Al-Khattab. I talked to him harshly and then regretted that, and requested him to forgive me, but he refused. This is why I have come to you." The Prophet said thrice, "O Abu Bakr! May Allah forgive you." In the meanwhile, `Umar regretted (his refusal of Abu Bakr's excuse) and went to Abu Bakr's house and asked if Abu Bakr was there. They replied in the negative. So he came to the Prophet and greeted him, but signs of displeasure appeared on the face of the Prophet till Abu Bakr pitied (`Umar), so he knelt and said twice, "O Allah's Apostle! By Allah! I was more unjust to him (than he to me)." The Prophet said, "Allah sent me (as a Prophet) to you (people) but you said (to me), 'You are telling a lie,' while Abu Bakr said, 'He has said the truth,' and consoled me with himself and his money." He then said twice, "Won't you then give up harming my companion?" After that nobody harmed Abu Bakr.