The Prophet ﷺ said: The witr is a duty for every Muslim so if anyone wishes to observe it with five rak'ahs, he may do so; if anyone wishes to observe it with three, he may do so, and if anyone wishes to observe it with one, he may do so.
قَالَ رَسُولُ اللَّهِ ﷺ الْوِتْرُ حَقٌّ عَلَى كُلِّ مُسْلِمٍ فَمَنْ أَحَبَّ أَنْ يُوتِرَ بِخَمْسٍ فَلْيَفْعَلْ وَمَنْ أَحَبَّ أَنْ يُوتِرَ بِثَلاَثٍ فَلْيَفْعَلْ وَمَنْ أَحَبَّ أَنْ يُوتِرَ بِوَاحِدَةٍ فَلْيَفْعَلْ