Musnad Abu Ya'la al-Mawsili 243:92

Abu Kurayb narrated to us, Abu Usamah narrated to us, from Burayd, from Abu Burdah, from Abu Musa, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) finished from Hunayn, he sent Abu Amir with an army to Awtas. He encountered Durayd ibn al-Simmah, and he killed Durayd, and Allah defeated his companions. Abu Musa said: And he sent me with Abu Amir. He said: Abu Amir was struck in his knee; a man from Banu Jusham shot him with an arrow, and it fixed itself in his knee. I reached him and said, "O uncle, who shot you?" Abu Amir pointed to Abu Musa, saying, "That is my killer, do you see him? That is the one who shot me." Abu Musa said: So I headed toward him and made for him, and I caught up with him. When he saw me, he turned away from me, fleeing. I followed him and began saying, "Do you not feel shame? Will you not stand firm? Do you not feel shame? Are you not an Arab?" So he stopped, and he and I met, and we exchanged two blows. I struck him with the sword and killed him. Then I returned to Abu Amir and said, "Allah has killed your assailant." He said, "Extract this arrow." So I extracted it, and water flowed from it. He said, "O son of my brother, go to the Messenger of Allah (peace and blessings of Allah be upon him), convey my greeting to him, and tell him that he says to you: 'Ask forgiveness for me.'" He said: Abu Amir appointed me as his successor, and he remained for a short while, then he died. When I returned to the Messenger of Allah (peace and blessings of Allah be upon him), I entered upon him while he was in a house on a bed, and the bed had left marks on the back and sides of the Messenger of Allah (peace and blessings of Allah be upon him). I informed him of our news and the news of Abu Amir, and I said, "He said: 'Ask forgiveness for me.'" He said: The Messenger of Allah (peace and blessings of Allah be upon him) called for water and performed ablution from it. Then he raised his hands and said, "O Allah, forgive Ubayd Abu Amir." Then he said, "O Allah, make him on the Day of Resurrection above many of Your creation and of the people." I said, "And for me, O Messenger of Allah, so ask for forgiveness." The Messenger of Allah (peace and blessings of Allah be upon him) said, "O Allah, forgive Abdullah ibn Qays his sin and admit him to a noble entrance." Abu Burdah said: One of them was for Abu Amir, and the other was for Abu Musa.