Musnad Ahmad 25:1451

Yazid narrated to us, he said: Muhammad—meaning Ibn Ishaq—said: Someone who heard ‘Ikrimah narrated to me, from Ibn ‘Abbas, who said: The one who captured al-‘Abbas ibn ‘Abd al-Muttalib was Abu al-Yusr ibn ‘Amr, and he is Ka‘b ibn ‘Amr, one of the Banu Salamah. The Messenger of Allah (peace and blessings of Allah be upon him) said to him: "How did you capture him, O Abu al-Yusr?" He said: "A man whom I have not seen before or after helped me against him; his appearance was such and such, his appearance was such and such." He said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A noble angel helped you against him." He said to al-‘Abbas: "O ‘Abbas, ransom yourself, and your nephew ‘Aqil ibn Abi Talib, and Nawfal ibn al-Harith, and your ally ‘Utbah ibn Jahdam," one of the Banu al-Harith ibn Fihr. He said: He refused and said: "I was a Muslim before that, and they only forced me." He said: "Allah knows best about your affair. If what you claim is true, then Allah will reward you for that. As for your outward affair, it was against us, so ransom yourself." The Messenger of Allah (peace and blessings of Allah be upon him) had taken twenty ounces of gold from him. He said: "O Messenger of Allah, count it for me as part of my ransom." He said: "No, that is something Allah gave us from you." He said: "I have no wealth." He said: "Where is the wealth that you deposited in Makkah when you left, with Umm al-Fadl, and there was no one with you two except you two? You said: 'If I am struck down in this journey of mine, then for al-Fadl is such and such, for Qutham is such and such, and for ‘Abdullah is such and such.'" He said: "By the One who sent you with the truth, no one among the people knew about this except me and her. I know that you are the Messenger of Allah."