Sahih Bukhari Volume 005, Book 057, Hadith Number 027.
Narated By 'Urwa bin Az-Zubair : I asked 'Abdullah bin 'Amr, "What was the worst thing the pagans did to Allah's Apostle?" He said, "I saw 'Uqba bin Abi Mu'ait coming to the Prophet while he was praying.' Uqba put his sheet round the Prophet's neck and squeezed it very severely. Abu Bakr came and pulled 'Uqba away from the Prophet and said, "Do you intend to kill a man just because he says: 'My Lord is Allah, and he has brought forth to you the Evident Signs from your Lord?"