Hadith 782:3
Hashim narrated to us, Ya'la ibn 'Ata' informed us, from 'Abd al-Rahman ibn Abi 'Abd al-Rahman, from 'Amr ibn 'Abasah, who said: I came to the Prophet, may Allah bless him and grant him peace, and said: "Who has followed you in this affair of yours?" He said: "A free man and a slave," meaning Abu Bakr and Bilal, may Allah be pleased with them both. 'Amr used to say after that: "I have seen myself, and I was one-fourth of Islam."
حدثنا هشيم، أخبرنا يعلى بن عطاء، عن عبد الرحمن بن أبي عبد الرحمن، عن عمرو بن عبسة، قال: أتيت النبي صلى الله عليه وسلم فقلت: من تابعك على أمرك هذا؟ قال: " حر وعبد " يعني أبا بكر وبلالا " رضي الله عنهما وكان عمرو يقول بعد ذلك: " فلقد رأيتني وإني لربع الإسلام "