Sahih Muslim 12111
In-book no 4834وَحَدَّثَنِيهِ مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الرَّحْمَنِ، حَدَّثَنَا سُفْيَانُ، بِهَذَا الإِسْنَادِ قَالَ عَبْدُ الرَّحْمَنِ قَالَ سُفْيَانُ لاَ أَدْرِي هَذَا فِي الْحَدِيثِ أَمْ لاَ . يَعْنِي أَنْ يَتَخَوَّنَهُمْ أَوْ يَلْتَمِسَ عَثَرَاتِهِمْ .
This tradition has been reported through anothee chain. 'Abdurahman, one of the sub-narrators, said "I do not know if it in the hadith or not", meaning (the words) "doubting their fidelity and spying into their lapses."