Messenger of Allah said: "When Fajr begins, then every Salat of the night and Al-Witr have gone, so perform Al-Witr before Fajr begins."

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا طَلَعَ الْفَجْرُ فَقَدْ ذَهَبَ كُلُّ صَلاَةِ اللَّيْلِ وَالْوِتْرُ فَأَوْتِرُوا قَبْلَ طُلُوعِ الْفَجْرِ