Ibn Abi Hatim al-Razi: He was a Companion, and narrated from him 'Urwa ibn al-Zubayr
Ibn Hajar al-'Asqalani: A well-known Companion. He said in al-Isabah: He embraced Islam on the day of the Conquest, and the Prophet, may God bless him and grant him peace, employed him as a scribe. He used to answer the kings on his behalf, and such was his trustworthiness in his eyes that he would order him to write to some kings, so he would write and seal it without reading it because of his trustworthiness. Then he wrote for Abu Bakr and 'Umar, and was in charge of the treasury during the time of 'Umar, and he was an Amir
al-Khatib al-Baghdadi: He was a Companion, and narrated from the Prophet, may God bless him and grant him peace
al-Dhahabi: One of the freedmen. He wrote the revelation, and was in charge of the treasury for 'Umar and 'Uthman without pay. Narrated from him Aslam and 'Urwa
Jalal al-Din al-Suyuti: He embraced Islam in the year of the Conquest, and wrote for the Prophet, may God bless him and grant him peace, then for Abu Bakr and 'Umar. Narrated from him Aslam, the freedman of 'Umar, and Abdullah ibn 'Utbah ibn Mas'ud and others