حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، قَالَ: حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ، قَالَ: أَخْبَرَنَا عَبْدُ اللهِ بْنُ عُثْمَانَ بْنِ عَبْدِ اللهِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ سَمُرَةَ، عَنْ بِلاَلِ بْنِ سَعْدٍ الأَشْعَرِيِّ، أَنَّ مُعَاوِيَةَ كَتَبَ إِلَى أَبِي الدَّرْدَاءِ: اكْتُبْ إِلَيَّ فُسَّاقَ دِمَشْقَ، فَقَالَ: مَا لِي وَفُسَّاقُ دِمَشْقَ؟ وَمِنْ أَيْنَ أَعْرِفُهُمْ؟ فَقَالَ ابْنُهُ بِلاَلٌ: أَنَا أَكْتُبُهُمْ، فَكَتَبَهُمْ، قَالَ: مِنْ أَيْنَ عَلِمْتَ؟ مَا عَرَفْتَ أَنَّهُمْ فُسَّاقٌ إِلاَّ وَأَنْتَ مِنْهُمْ، ابْدَأْ بِنَفْسِكَ، وَلَمْ يُرْسِلْ بِأَسْمَائِهِمْ.
Bilal ibn Sa'd al-Ash'ari related that Mu'awiya wrote to Abu Dharr, "Write down for me the deviants of Damascus." Abu Dharr said, "What do I have to do with the deviants of Damascus and how would I know them?" His son Bilal said, "I will write them," so he wrote them. Abu Dharr said, "How do you know? You would only know that they are deviants if you were one of them. Begin with yourself and do not send their names."
Cited in Al-Adab al-Mufrad (No. 1290).