Maliks Muwatta Book 050, Hadith Number 006.

Section : The Reward of the Invalid.

Yahya related to me from Malik from Yazid ibn Khusayfa that Urwa ibn az-Zubayr said that he heard A'isha, the wife of the Prophet, may Allah bless him and grant him peace, say, "The Messenger of Allah, may Allah bless him and grant him peace, said, 'When a mumin is afflicted by something, even a thorn, it removes (or effaces) his wrong actions.'" Yazid did not know which of them Urwa said.