Musnad Ahmad 1153:867

'Ali ibn Ishaq narrated to us, he said: 'Abdullah informed us, he said: Yunus informed us, from al-Zuhri, he said: 'Urwah ibn al-Zubayr narrated to me, from 'Aishah, she said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no calamity that befalls a Muslim but that it is an expiation for him, even the thorn with which he is pricked."