Musnad Ahmad 992:1

'Abd al-Rahman ibn Mahdi narrated to us, from Zuhayr, from al-'Ala', from Abu Kathir, the freed slave of Muhammad ibn 'Abd Allah ibn Jahsh, who said: Muhammad ibn 'Abd Allah ibn Jahsh informed me, saying: We were sitting in the courtyard of the mosque where the funeral biers are placed, and the Messenger of Allah (peace and blessings of Allah be upon him) was sitting among us. The Messenger of Allah (peace and blessings of Allah be upon him) raised his gaze toward the sky and looked, then he lowered his gaze and placed his hand upon his forehead. Then he said: "Glory be to Allah, glory be to Allah! What has been revealed of severity?" He said: So we remained silent for our day and our night, and we did not see anything but good until we reached the morning. Muhammad said: So I asked the Messenger of Allah (peace and blessings of Allah be upon him): "What is the severity that was revealed?" He said: "Regarding debt. By the One in Whose hand is the soul of Muhammad, if a man were killed in the way of Allah, then lived, then were killed in the way of Allah, then lived, then were killed in the way of Allah, then lived, while he had a debt upon him, he would not enter Paradise until his debt is paid off."