Musannaf Ibn Abi Shaybah

Hazrat Yazid bin Amr Mu'afiri says that I heard Abu Thawr Fahmi say: Hazrat Abdur Rahman bin 'Adis Balawi came to us. He was among those who pledged allegiance to the Prophet (peace be upon him) under the tree. He ascended the pulpit and praised Allah Almighty, then mentioned Hazrat Uthman: Hazrat Abu Thawr says that I was present with Hazrat Uthman when he was besieged. He said: I am the fourth person to accept Islam.