Musnad Ahmad 32:462

Hashim and ‘Affan narrated to us—the meaning is the same—they said: Sulayman narrated to us, from Thabit, who said: We were with Anas ibn Malik, and he wrote a document for his family. He said: "Bear witness, O company of the reciters (Qurra’)." Thabit said: It was as if I disliked that, so I said: "O Abu Hamzah, if only you had named them by their names." He said: "What is the harm in me calling you 'reciters'? Shall I not tell you about your brothers whom we used to call 'the reciters' during the time of the Messenger of Allah (ﷺ)?" He mentioned that they were seventy. When night would cover them, they would go to a place of learning for them in Medina, and they would study the Quran in it until morning. When morning came, whoever had strength would fetch sweet water and gather firewood, and whoever had means would gather together, and they would buy a sheep and prepare it, and it would be hung in the quarters of the Messenger of Allah (ﷺ). When Khubayb was struck [killed], the Messenger of Allah (ﷺ) sent them. They came upon a tribe from Banu Sulaym, among whom was my maternal uncle, Haram. Haram said to their leader: "Let me go, so I may inform these people that we do not intend [to fight] them, until they let us pass." ('Affan said: "Until they let us pass.") Haram said to them: "We do not intend [to fight] you." A man met him with a spear and pierced him through with it. When he felt the spear in his belly, he said: "Allah is the Greatest! I have succeeded, by the Lord of the Kaaba." He said: Then they fell upon them, and not one of them remained. Anas said: "I never saw the Messenger of Allah (ﷺ) grieve over anything as he grieved over them. I saw the Messenger of Allah (ﷺ), every time he prayed the morning prayer, he would raise his hands and supplicate against them." Sometime after that, Abu Talhah said to me: "Would you like to see the killer of Haram?" I said to him: "What is it to him? May Allah do to him such and such." He said: "Softly, for he has accepted Islam." 'Affan said: "He raised his hands supplicating against them." And Abu al-Nadr said: "He raised his hands."