Ibn 'Umar said:

A man who lived in the desert asked the Messenger of Allah (ﷺ) about the prayer at night. He made a sign with his two fingers-in this way in pairs. The witr consists of one rak'ah towards the end in night.

حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، أَخْبَرَنَا هَمَّامٌ، عَنْ قَتَادَةَ، عَنْ عَبْدِ اللَّهِ بْنِ شَقِيقٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَجُلاً، مِنْ أَهْلِ الْبَادِيَةِ سَأَلَ النَّبِيَّ صلى الله عليه وسلم عَنْ صَلاَةِ اللَّيْلِ فَقَالَ بِأُصْبُعَيْهِ هَكَذَا مَثْنَى مَثْنَى وَالْوِتْرُ رَكْعَةٌ مِنْ آخِرِ اللَّيْلِ ‏.‏