"I asked 'Aishah about the prayer of the Messenger of Allah ﷺ. She said: 'He used to sleep during the first part of the night, then get up during the time before dawn and pray witr. Then he would go to his bed and if he needed to be intimate he would go to his wife. Then when he heard the Adhan he would get up, and if he was junub he would pour water over himself, otherwise he would perform wudu, then he would go out to the prayer.'" (Using translation from Nasāʾī 1680)  

عَنْ صَلَاةِ رَسُولِ اللهِ ﷺ قَالَتْ كَانَ «يَنَامُ أَوَّلَ اللَّيْلِ ثُمَّ يَقُومُ فَإِذَا كَانَ مِنَ السَّحَرِ أَوْتَرَ وَأَتَى فِرَاشَهُ فَإِنْ كَانَتْ لَهُ حَاجَةً أَلَمَّ بِأَهْلِهِ فَإِذَا سَمِعَ الْأَذَانَ وَثَبَ فَإِنْ كَانَ جُنُبًا أَفَاضَ عَلَيْهِ مِنَ الْمَاءِ وَإِلَّا تَوَضَّأَ ثُمَّ خَرَجَ إِلَى الصَّلَاةِ»  

"The Messenger of Allah ﷺ prayed witr at the beginning (of the night) and at the end, and in the middle. And toward the end of his life, he settled on performing witr at the end of the night." (Using translation from Nasāʾī 1681)  

«أَوْتَرَ رَسُولُ اللهِ ﷺ مِنْ كُلِّ اللَّيْلِ مِنْ أَوَّلِهِ وَآخِرِهِ وَأَوْسَطِهِ وَانْتَهَى وِتْرُهُ إِلَى السَّحَرِ»  

He who prayed at night should make Witr the end of his prayer, for the Messenger of Allah ﷺ ordered this. (Using translation from Muslim 751a)  

«مَنْ صَلَّى مِنَ اللَّيْلِ فَلْيَجْعَلْ آخِرَ صَلَاتِهِ وِتْرًا فَإِنَّ رَسُولَ اللهِ ﷺ كَانَ يَأْمُرُ بِذَلِكَ»