Musnad Ahmad 30:1252

Uthman ibn Umar narrated to us, Abd al-Hamid ibn Ja'far narrated to us, from Iyad ibn Abdullah ibn Abi Sarh, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) stood and addressed the people. He mentioned that faith in Allah and Jihad in the cause of Allah are among the best of deeds in the sight of Allah. A man stood up and said: "O Messenger of Allah, if I am killed in the cause of Allah, while I am patient and seeking reward, advancing and not retreating, will Allah expiate my sins for me?" He said: "Yes. But what did you say?" He said: "If I am killed in the cause of Allah, while I am patient and seeking reward, advancing and not retreating, will Allah expiate my sins for me?" He said: "Yes. What did you say?" He said: "If I am killed in the cause of Allah, while I am patient and seeking reward, advancing and not retreating, will Allah expiate my sins for me?" He said: "Yes, except for debt, for Jibril whispered that to me."