The Book of Repentance
قَالَ أَبُو أَحْمَدَ حَدَّثَنِي مُحَمَّدُ بْنُ زَنْجُويَهْ الْقُرَشِيُّ الْقُشَيْرِيُّ، حَدَّثَنَا عَبْدُ الأَعْلَى، بْنُ حَمَّادٍ النَّرْسِيُّ بِهَذَا الإِسْنَادِ .The hadlth has been narrated on the authority of 'Abd al-A'la b. Hammad with the same chain of transmitters
From Sahih Muslim, whose reports the scholars accept as authentic.