Musannaf Ibn Abi Shaybah

Hazrat Aamir narrates that I asked Ibn Abbas (may Allah be pleased with them both), or it is said: Ibn Abbas (may Allah be pleased with them both) was asked: Who among the people was the first to accept Islam? He replied: Have you not heard the saying of Hassan bin Thabit: "When you remember the sorrow that has reached you from your trusted brother, then remember what your brother Abu Bakr did, who is the best among creation, the greatest God-fearing and just, except for the Prophet, and the one who fulfills his responsibilities. And the other (believer) is a follower, and his testimony is commendable. And among the people, he was the first to affirm the Messenger."