Musnad Abu Ya'la al-Mawsili 150:334

Harun ibn Ma'ruf narrated to us, Abu Abd al-Rahman narrated to us, Sa'id narrated to us, 'Aqil and Yunus narrated to me, from Ibn Shihab, from Abu Salamah ibn Abd al-Rahman, from 'Aishah, that she said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever from my Ummah bears a debt, then strives to pay it off, but dies before he pays it off, then I am his guardian."