The Book of Repentance
وَحَدَّثَنَاهُ مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، حَدَّثَنَا الْمُعْتَمِرُ، عَنْ أَبِيهِ، بِهَذَا الإِسْنَادِ .This hadith has been transmitted on the authority of Mu'tamir, reported on the authority of his father
From Sahih Muslim, whose reports the scholars accept as authentic.