Sahih al-Bukhari Book 62, Hadith 12
I saw Allah's Messenger (ﷺ) and there was none with him but five slaves, two women and Abu Bakr (i.e.
those were the only converts to Islam then).
A woman came to the Prophet (ﷺ) who ordered her to return to him again. She said, "What if I came and did not find you?" as if she wanted to say, "If I found you dead?" The Prophet (ﷺ) said, "If you should not find me, go to Abu Bakr."
While I was sitting with the Prophet, Abu Bakr came, lifting up one corner of his garment uncovering his knee. The Prophet (ﷺ) said, "Your companion has had a quarrel." Abu Bakr greeted (the Prophet (ﷺ) ) and said, "O Allah's Messenger (ﷺ)! 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 (ﷺ) 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 (ﷺ) and greeted him, but signs of displeasure appeared on the face of the Prophet (ﷺ) till Abu Bakr pitied (`Umar), so he knelt and said twice, "O Allah's Messenger (ﷺ)! By Allah! I was more unjust to him (than he to me)." The Prophet (ﷺ) 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.