Musnad Abu Ya'la al-Mawsili 245:8

Abu Hammam narrated to us, al-Walid ibn Muslim narrated to us, he said: Abd al-Rahman ibn Yazid ibn Jabir narrated to me, he said: Ibn Abi al-Muhajir or Abu Abd Rabb al-Walid—he was in doubt—narrated to me, he said: I heard Mu'awiyah ibn Abi Sufyan saying: I heard the Messenger of Allah (ﷺ) saying: "A man from among those who were before you met a man who was a scholar or a worshiper. He said: 'The other has killed ninety-nine souls, all of which he killed unjustly. Do you find any repentance for me?' He said: 'No.' So he killed him. Then he met another and said: 'The other has killed one hundred souls, all of which he killed unjustly. Do you find any repentance for me?' He said: 'If I were to tell you that Allah, the Mighty and Majestic, does not accept the repentance of one who repents, I would have lied. Over there is a monastery in which there are people who worship; go to them and worship Allah with them, perhaps Allah will accept your repentance.' So he set off toward them, but he died before he reached them. The angels of punishment and the angels of mercy disputed. Allah sent an angel, saying: 'Measure between the two places; whichever one he was closer to, he belongs to it.' They measured and found him closer to the monastery of the repentant by a fingertip, so Allah forgave him."