Sahih Bukhari Volume 009, Book 085, Hadith Number 075.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 85. Saying Something under Compulsion (Ikraah)
Narrated By Qais : I heard Sa'id bin Zaid saying, "I have seen myself tied and forced by 'Umar to leave Islam (Before 'Umar himself embraced Islam). And if the mountain of Uhud were to collapse for the evil which you people had done to 'Uthman, then Uhud would have the right to do so." (See Hadith No. 202, Vol. 5)