أَخْبَرَنَا هَارُونُ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا حَجَّاجٌ، قَالَ قَالَ ابْنُ جُرَيْجٍ عَنْ أَبِيهِ، أَخْبَرَنِي ابْنُ أَبِي مُلَيْكَةَ، أَنَّ يَعْلَى بْنَ مَمْلَكٍ، أَخْبَرَهُ أَنَّهُ، سَأَلَ أُمَّ سَلَمَةَ عَنْ صَلاَةِ، رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَتْ كَانَ يُصَلِّي الْعَتَمَةَ ثُمَّ يُسَبِّحُ ثُمَّ يُصَلِّي بَعْدَهَا مَا شَاءَ اللَّهُ مِنَ اللَّيْلِ ثُمَّ يَنْصَرِفُ فَيَرْقُدُ مِثْلَ مَا صَلَّى ثُمَّ يَسْتَيْقِظُ مِنْ نَوْمِهِ ذَلِكَ فَيُصَلِّي مِثْلَ مَا نَامَ وَصَلاَتُهُ تِلْكَ الآخِرَةُ تَكُونُ إِلَى الصُّبْحِ .
Ya'la bin Mamlak said that he asked Umm Salamah about the prayer of the Messenger of Allah (PBUH) and she said: "He used to pray 'Isha, then he would recite tasbih, then after that he would pray whatever Allah (SWT) willed (he should pray) of night prayer. Then he would go and sleep for as long as he had prayed. Then he would get up from sleep and pray for as long as he had slept, and this last prayer of his would continue until dawn." Translation Not Available
Book Ref: Sunan An Nisai Book 20 Hadith 1628
Web Ref: Sunan An Nisai Vol 2 Book 20 Hadith 1629