Musannaf Ibn Abi Shayba 19:248

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Isma’il bin Umayyah, from Sa’d bin Ibrahim, from his father, he said: I remember the skin of a sheep that I ordered to be slaughtered when ‘Umar struck Abu Bakrah. Its skin was placed upon his back due to the severity of the striking.