He who observed the night prayer should make Witr the end of his prayer before dawn. The Messenger of Allah ﷺ used to order them thus.  

أَنَّ ابْنَ عُمَرَ كَانَ يَقُولُ مَنْ صَلَّى مِنَ اللَّيْلِ فَلْيَجْعَلْ آخِرَ صَلاَتِهِ وِتْرًا قَبْلَ الصُّبْحِ كَذَلِكَ كَانَ رَسُولُ اللَّهِ ﷺ يَأْمُرُهُمْ  

[Machine] "Narrated Ibn Umar that he used to say: 'Whoever prays at night, let him make Witr as his last prayer. For indeed, the Messenger of Allah ﷺ commanded that. And when dawn comes, all the night prayers and Witr are gone. For indeed, the Messenger of Allah ﷺ said: 'Perform Witr before dawn.'  

أَنَّ ابْنَ عُمَرَ كَانَ يَقُولُ مَنْ صَلَّى بِاللَّيْلِ فَلْيَجْعَلْ آخِرَ صَلَاتِهِ وِتْرًا فَإِنَّ رَسُولَ اللهِ ﷺ أَمَرَ بِذَلِكَ فَإِذَا كَانَ الْفَجْرُ فَقَدْ ذَهَبَتْ كُلُّ صَلَاةِ اللَّيْلِ وَالْوَتْرُ فَإِنَّ رَسُولَ اللهِ ﷺ قَالَ أَوْتِرُوا قَبْلَ الْفَجْرِ  

He who observed the night prayer should make Witr the end of his prayer before dawn. The Messenger of Allah ﷺ used to order them thus. (Using translation from Muslim 751c)  

أَنَّ ابْنَ عُمَرَ كَانَ يَقُولُ مَنْ صَلَّى مِنَ اللَّيْلِ فَلْيَجْعَلْ آخِرَ صَلَاتِهِ وِتْرًا قَبْلَ الصُّبْحِ كَذَلِكَ كَانَ رَسُولُ اللهِ ﷺ يَأْمُرُهُمْ  

[Machine] Ibn 'Umar used to say: "Whoever prays at night should make his last prayer odd number of units, for the Messenger of Allah ﷺ ordered that. When dawn breaks, the night prayer and the witr prayer are no longer valid, because the Messenger of Allah ﷺ said: 'Perform the witr prayer before dawn.' And in another narration: 'Perform the witr prayer with the dawn prayer.'"  

أَنَّ ابْنَ عُمَرَ كَانَ يَقُولُ مَنْ صَلَّى مِنَ اللَّيْلِ فَلْيَجْعَلْ آخِرَ صَلَاتِهِ وِتْرًا فَإِنَّ رَسُولَ اللهِ ﷺ أَمَرَ بِذَلِكَ فَإِذَا كَانَ الْفَجْرُ فَقَدْ ذَهَبَ صَلَاةُ اللَّيْلِ وَالْوِتْرُ؛ لِأَنَّ رَسُولَ اللهِ ﷺ قَالَ الْوِتْرُ قَبْلَ الْفَجْرِ وَفِي رِوَايَةِ الْفَحَّامِ قَالَ أَوْتِرُوا بِالْفَجْرِ