حَدَّثَنَا عَبْدُ اللهِ بْنُ مُحَمَّدٍ، قَالَ: حَدَّثَنَا أَبُو عَامِرٍ، قَالَ: حَدَّثَنَا عَبْدُ الْجَلِيلِ بْنُ عَطِيَّةَ، عَنْ شَهْرٍ، عَنْ أُمِّ الدَّرْدَاءِ قَالَتْ: قَامَ أَبُو الدَّرْدَاءِ لَيْلَةً يُصَلِّي، فَجَعَلَ يَبْكِي وَيَقُولُ: اللَّهُمَّ أَحْسَنْتَ خَلْقِي فَحَسِّنْ خُلُقِي، حَتَّى أَصْبَحَ، قُلْتُ: يَا أَبَا الدَّرْدَاءِ، مَا كَانَ دُعَاؤُكَ مُنْذُ اللَّيْلَةِ إِلاَّ فِي حُسْنِ الْخُلُقِ؟ فَقَالَ: يَا أُمَّ الدَّرْدَاءِ، إِنَّ الْعَبْدَ الْمُسْلِمَ يَحْسُنُ خُلُقُهُ، حَتَّى يُدْخِلَهُ حُسْنُ خُلُقِهِ الْجَنَّةَ، وَيَسِيءُ خُلُقُهُ، حَتَّى يُدْخِلَهُ سُوءُ خُلُقِهِ النَّارَ، وَالْعَبْدُ الْمُسْلِمُ يُغْفَرُ لَهُ وَهُوَ نَائِمٌ، قُلْتُ: يَا أَبَا الدَّرْدَاءِ، كَيْفَ يُغْفَرُ لَهُ وَهُوَ نَائِمٌ؟ قَالَ: يَقُومُ أَخُوهُ مِنَ اللَّيْلِ فَيَجْتَهِدُ فَيَدْعُو اللَّهَ عَزَّ وَجَلَّ فَيَسْتَجِيبُ لَهُ، وَيَدْعُو لأَخِيهِ فَيَسْتَجِيبُ لَهُ فِيهِ.
Umm ad-Darda' said, "Abu'd-Darda' stood up in the night to pray. He was weeping and said, 'O Allah! You made my physical form good, so make my character good!' until morning. I said, 'Abu'd-Darda', your only supplication for the entire night was for good character!' He replied, 'Umm ad-Darda', the Muslim perfects his character until good character enters him into Paradise; and taints his character until his bad character enter him into Hellfire. The Muslim is forgiven while he is asleep.' I asked, 'Abu'd-Darda', how can be forgiven while he is asleep?' He said, 'His brother arises in the night, performs the night prayer, and supplicates to Allah Almighty and is answered. He supplicates for his Muslim brother and his supplication is answered.'"
Cited in Al-Adab al-Mufrad (No. 290).