أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ، قَالَ حَدَّثَنَا يَحْيَى، قَالَ حَدَّثَنَا زُهَيْرٌ، عَنْ أَبِي إِسْحَاقَ، قَالَ أَتَيْتُ الأَسْوَدَ بْنَ يَزِيدَ وَكَانَ لِي أَخًا صَدِيقًا فَقُلْتُ يَا أَبَا عَمْرٍو حَدِّثْنِي مَا حَدَّثَتْكَ بِهِ أُمُّ الْمُؤْمِنِينَ عَنْ صَلاَةِ رَسُولِ اللَّهِ صلى الله عليه وسلم . قَالَ قَالَتْ كَانَ يَنَامُ أَوَّلَ اللَّيْلِ وَيُحْيِي آخِرَهُ .
It was narrated that Abu Ishaq said: "I came to Al-Aswad bin Yazid, who was a close friend of mine and said: 'O Abu 'Amr, tell me what the Mother of the Believers told you about the prayer of the Messenger of Allah (PBUH).' He said: 'She said: "He used to sleep for the first part of the night and stay up for the latter part.'" Translation Not Available
Book Ref: Sunan An Nisai Book 20 Hadith 1640
Web Ref: Sunan An Nisai Vol 2 Book 20 Hadith 1641