We were at al-Baqi with Abu Hurairah when we heard him say, "I know best among people about the intercession of Muhammad ﷺ on the Day of Resurrection."The people crowded around him and said, "Go on, may Allah have mercy on you!"He said, "He will say, 'O Allah, forgive every Muslim servant who meets You believing in me, not associating anything with You.'"
إنا بالبقيع مع أبي هريرة إذ سمعناه يقول: أنا أعلم الناس بشفاعة لمحمد ﷺ يوم القيامة، قال: فتداك الناس عليه، فقالوا: إيه يرحمك الله! قال: يقول: اللهم اغفر لكل عبد مسلم، لقيك يؤمن بي لا يشرك بك.
Ahmad (9852) narrated it from Hajjaj, who said, Ibn Jurayj told us, who said, Ala bin Abdul-Rahman bin Yaqub told me, from Ibn Darah, the freed slave of Uthman, and he mentioned it. Its chain is hasan on account of Ala bin Abdul-Rahman and his teacher Ibn Darah, the freed slave of Uthman, both of whom are hasan al-hadith. There is disagreement about whether Ibn Darah was a companion or not, and the correct view is that he was not a companion.