Abdullah bin Masud reported,

The first to openly declare their Islam were seven, the Messenger of Allah ﷺ, Abu Bakr, Ammar, his mother Sumayy, Suhayb, Bilal, and Miqdad.As for the Messenger of Allah ﷺ, Allah protected him through his uncle Abu Talib. As for Abu Bakr, Allah protected him through his clan. As for the rest, the polytheists seized them, clothed them in iron armor, and scorched them in the sun. Every one of them gave in to what their tormentors demanded, except Bilal. He considered his own life of little worth for the sake of Allah, and his people considered him of little worth as well, so they handed him over to the boys, who began parading him through the mountain passes of Makkah while he was saying, "One, One."

عن عبد الله بن مسعود قال

أول من أظهر إسلامه سبعة: رسول الله ﷺ، وأبو بكر، وعمار، وأمه سمية، وصهيب، وبلال والمقداد. فأما رسول الله ﷺ فمنعه الله بعمه أبي طالب، وأما أبو بكر فمنعه الله بقومه، وأما سائرهم فأخذهم المشركون، فألبسوهم أذراع الحديد، وصهرهم في الشمس، فما منهم إنسان إلا وقد وأتاهم على ما أرادوا إلا بلال، فإنه هانت عليه نفسه في الله، وهان على قومه، فأعطوه الولدان، وأخذوا يطوفون به شعاب مكة. وهو يقول: أحد أحد.