Musnad Ahmad 1153:148

Husayn narrated to us, Shayban narrated to us, from Mansur, from Ibrahim, from al-Aswad, from Aisha, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "There is no believer who is pricked by a thorn or anything above it, except that a degree is written for him because of it, and a sin is expiated from him because of it."