He heard the Prophet ﷺ saying during a prayer, "My Lord, forgive me," or he said, "O Allah, forgive me and accept my repentance. You are the Ever-Relenting, the Most Forgiving," one hundred times.
أنه سمع النبي ﷺ في صلاة وهو يقول: رب اغفر لي- أو قال اللهم اغفر لي- وتب علي، إنك أنت التواب الغفور مائة مرة.
Imam Ahmad (23150) and Nasai in Al-Kubra (9852) both narrated it through Shubah, from Husayn, from Hilal bin Yasaf, from Zazan, from a man among the companions of the Prophet ﷺ, and he related it.Its chain of transmission is hasan because of Zazan, who is Abu Umar Kindi, for his hadith is hasan. Husayn is Ibn Abdul-Rahman Sulami, Abu Huzayl Kufi, trustworthy, though he became confused in his memory toward the end of his life. However, Shubah's narration from him was before this confusion set in.Khalid bin Abdullah Wasiti differed from him, narrating it from Husayn, from Hilal bin Yasaf, from Zazan, from Ayesha, and he related it. Nasai narrated this in Al-Kubra (9855), making it part of the musnad of Ayesha.Nasai said after it, "The hadith of Shubah, Abdul-Aziz bin Muslim, and Abbad bin Awwam is, in our view, more likely to be correct than the hadith of Khalid, and success comes from Allah. Husayn bin Abdul-Rahman had indeed become confused toward the end of his life."I say, it is as he said, but Shubah's narration from him was before this confusion, as I have shown.