Musnad Ahmad 28:573

Yahya ibn Ghaylan narrated to us, al-Mufaddal narrated to me, 'Ayyash ibn 'Abbas narrated to me, from 'Abdullah ibn Yazid Abu 'Abd al-Rahman al-Hubuli, from 'Abdullah ibn 'Amr ibn al-'As, that the Messenger of Allah (may Allah bless him and grant him peace) said: "Every sin of the martyr is forgiven, except for debt."