Sayyiduna Abdullah (may Allah be pleased with him) said: I reached Abu Jahl while he was lying half dead. He had a helmet on his head and a fine sword with him, while my sword was poor. I struck his head with my sword, and at that moment I remembered how he used to beat me in Makkah. I struck him until his hand weakened, then I took hold of his sword. He raised his head and said: "Who suffered defeat, us or them?" And he said to me: "Were you not our little shepherd in Makkah?" Sayyiduna Abdullah (may Allah be pleased with him) said: I killed him. Then I came to the Prophet (peace and blessings be upon him) and said: "I have killed him." The Prophet (peace and blessings be upon him) said: "By Allah, besides whom there is no god (worthy of worship), did you kill him?" The Prophet (peace and blessings be upon him) made me swear three times; then he went with me, and then he supplicated against them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18013