Narrated by Abu Ad-Darda (RA) :

While I was sitting with Allaah’s Messenger (SAW), Abu Bakr (RA) came, lifting up one corner of his garment uncovering his knee.

Allaah’s Messenger (SAW) said :

Your companion has had a quarrel.

Abu Bakr (RA) greeted Allaah’s Messenger (SAW) and said :

O Allaah’s Messenger ! 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.

Allaah’s Messenger (SAW) 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 Allaah’s Messenger (SAW) and greeted him, but signs of displeasure appeared on the face of Allaah’s Messenger (SAW) till Abu Bakr (RA) pitied ‘Umar (RA), so he knelt and said twice :

O Allaah’s Messenger ! By Allaah ! I was more unjust to him (than he to me).

Allaah’s Messenger (SAW) said :

Allaah 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 (RA).

[ Sahih Al-Bukhari, The Book of the Companions of the Prophet, No. 3412 ]