Abu Dawud Book 19, Hadith Number 3641.
Chapter : Writing the knowledge.
Narated By Abu Hurairah : When Mecca was conquered, the Holy Prophet (PBUH) stood up. He (Abu Hurairah) then mentioned the sermon of the Holy Prophet (PBUH). He said: A man of the Yemen, who was called Abu Shah, got up and said: Apostle of Allah! write it for me. He said: Write it for Abu Shah.