Musnad Ahmad 1065:16

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 narrated to me, from Abu Sufyan, the freed slave of [Ibn] Abi Ahmad, from Abu Hurayrah, who said: He used to say: "Tell me about a man who entered Paradise without ever having performed a prayer." If the people did not know him, they would ask him: "Who is he?" He would say: "Usayrim of Banu 'Abd al-Ashhal, 'Amr ibn Thabit ibn Waqsh." Al-Husayn said: I said to Mahmud ibn Labid: "What was the affair of the Usayrim?" He said: "He used to refuse Islam to his people. When the day of Uhud came and the Messenger of Allah, peace and blessings of Allah be upon him, went out to Uhud, Islam appeared to him, so he accepted Islam. He took his sword and set out early until he reached the people and entered into the midst of them. He fought until wounds incapacitated him." He said: While the men of Banu 'Abd al-Ashhal were searching for their dead on the battlefield, they came upon him. They said: "By Allah, this is the Usayrim! What brought him here? We left him while he was rejecting this matter." They asked him what brought him. They said: "What brought you, O 'Amr? Is it out of sympathy for your people, or out of desire for Islam?" He said: "Rather, it is out of desire for Islam. I believed in Allah and His Messenger, and I accepted Islam. Then I took my sword and set out early with the Messenger of Allah, and I fought until what has befallen me befell me." He said: Then he did not linger before he died in their hands. They mentioned him to the Messenger of Allah, peace and blessings of Allah be upon him, and he said: "He is indeed among the people of Paradise."