عَنْ نَافِعٍ أَنَّ ابْنَ عُمَرَ رَضِيَ اللَّهُ عَنْهُ كَانَ يَقُولُ: مَنْ صَلَّى بِاللَّيْلِ فَلْيَجْعَلْ آخِرَ صَلَاتِهِ وَتْرًا، فَإِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ أَمَرَ بِذَلِكَ، فَإِذَا كَانَ الْفَجْرُ فَقَدْ ذَهَبَتْ كُلُّ صَلَاةِ اللَّيْلِ وَالْوِتْرُ، فَإِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ: ((أَوْتِرُوا قَبْلَ الْفَجْرِ))
It is narrated from Hazrat Nafi that Sayyiduna Abdullah bin Umar, may Allah be pleased with him, used to say that whoever prays at night should perform Witr at the end, because the Messenger of Allah, peace and blessings be upon him, has given this command. And when Fajr begins, all the night prayer and the time for Witr ends, because the Messenger of Allah, peace and blessings be upon him, said: Perform Witr before Fajr.