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 (ﷺ).' He said: 'She said: "He used to sleep for the first part of the night and stay up for the latter part.'"
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 .
Nesai
The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day • Hadith 1640