Musnad Ahmad 1065:1

Ya'qub ibn Ibrahim narrated to us, my father narrated to us, from Ibn Ishaq, Al-Husayn ibn Abd al-Rahman ibn 'Amr ibn Sa'd ibn Mu'adh, brother of the Banu 'Abd al-Ashhal, narrated to me, from Mahmud ibn Labid, brother of the Banu 'Abd al-Ashhal, who said: When Abu al-Haysar Anas ibn Rafi' came to Makkah, and with him were youths from the Banu 'Abd al-Ashhal, among them Iyas ibn Mu'adh, seeking an alliance from Quraysh against their people, the Khazraj, the Messenger of Allah (peace be upon him) heard of them. He came to them and sat with them, then said to them: "Do you desire something better than what you have come for?" They said: "And what is that?" He said: "I am the Messenger of Allah. He sent me to the servants to call them to worship Allah and not associate anything with Him, and He revealed a Book to me." Then he mentioned Islam and recited the Quran to them. Iyas ibn Mu'adh, who was a young boy, said: "O my people, by Allah, this is better than what you have come for." Abu al-Haysar Anas ibn Rafi' took a handful of gravel and struck Iyas ibn Mu'adh in the face with it. The Messenger of Allah (peace be upon him) stood up from them, and they departed for Madinah. Then the Battle of Bu'ath took place between the Aws and the Khazraj. Mahmud ibn Labid said: Those of my people who were present at his death informed me that they did not cease hearing him declaring the oneness of Allah (tahlil), magnifying Him (takbir), praising Him (tahmid), and glorifying Him (tasbih) until he died. They did not doubt that he had died a Muslim; he had indeed embraced Islam in that gathering when he heard from the Messenger of Allah (peace be upon him) what he heard.