Al-Matalib al-'Aliyah 3816 — Allah informing the Prophet ﷺ

It is narrated from Abdullah bin Abi Bakr (may Allah have mercy on him) that Sayyiduna Abu Sufyan (may Allah be pleased with him) was sitting in a corner of the mosque when the Prophet (peace and blessings be upon him) came out from the house of one of his pure wives, wrapped in his blessed sheet. Sayyiduna Abu Sufyan (may Allah be pleased with him), sitting in his place, said (to himself): "If only I knew on what basis you have prevailed over me?" The Prophet (peace and blessings be upon him) turned towards him until he patted him on the back with his blessed hand, and then said: "I prevailed over you through the help and grace of Allah, the Mighty and Majestic." At this Sayyiduna Abu Sufyan (may Allah be pleased with him) exclaimed: "I bear witness that you are indeed the Messenger of Allah."
Imam al-Harith narrated this hadith in his Musnad (Bughyat al-Bahith: 832); this narration is mursal, and all its narrators are thiqat (trustworthy).