Musnad Ahmad 31:770

Ya'qub narrated to us, my father narrated to us, from Muhammad ibn Ishaq, Muhammad ibn 'Amr ibn 'Ata' narrated to me, that 'Ata' ibn Yasar narrated to him, that Abu Sa'id al-Khudri narrated to him, that he heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "No fatigue, nor disease, nor illness, nor sadness, nor harm befalls a believer, not even the worry that concerns him, but that Allah expiates some of his sins for it."