Aswad bin Khalaf saw the Prophet ﷺ taking the people's pledge of allegiance on the day of the Conquest. He said that the Prophet ﷺ sat by the projection of Masqalah and took the pledge of the people upon Islam and the testimony.I asked, "What is the testimony?"He replied, "Muhammad bin Aswad bin Khalaf informed me that he took their pledge upon belief in Allah and the testimony that there is no god but Allah and that Muhammad is His servant and messenger ﷺ."
حدثنا عبد الرزاق أخبرنا ابن جريج قال أخبرني عبد الله بن عثمان بن خثيم أن محمد بن الأسود بن خلف أخبره أن
رأى النبي ﷺ يبايع الناس يوم الفتح قال جلس عند قرن مسقلة فبايع الناس على الإسلام والشهادة قال قلت وما الشهادة قال أخبرني محمد بن الأسود بن خلف أنه بايعهم على الإيمان بالله وشهادة أن لا إله إلا الله وأن محمدا عبده ورسوله ﷺ
Its isnad is sahih. Muhammad bin Aswad bin Khalaf was deemed trustworthy by Ibn Hibban, Bukhari was silent about him, and no one criticized him. Hakim narrated the hadith in Marifat al-Sahaba 3/296. His statement "qarn mustaqillah" or "musaqqilah" refers to a place in the Kaaba.