Abi Nadrah AI-'Awfee RA. reports:
"I asked Abu Sa'eed Khudari Radiyallahu 'Anhu about the Seal of Prophethood of Rasulullah sallailahu 'Alayhi Wasallam. He said: 'It was a piece of raised flesh that was on Rasulullah Sallallahu 'Alayhi Wasallam's back".
English reference: Book 2, Hadith 21
Arabic reference: Book 2, Hadith 22