(20) The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
كتاب قيام الليل وتطوع النهار
(41) Chapter: How to pray witr with five rak'ahs, and the differences reported from Al-Hakam in the hadith about Witr
(41) باب كَيْفَ الْوِتْرُ بِخَمْسٍ وَذِكْرِ الاِخْتِلاَفِ عَلَى الْحَكَمِ فِي حَدِيثِ الْوِتْرِ
Sunan an-Nasa'i 1714 
Mansur reported from Al-Hakam, from Miqsam, that Umm Salamah said:
"The Messenger of Allah (ﷺ) used to pray witr with five and seven rak'ahs which he did not separate with any taslim nor talk."
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنِ الْحَكَمِ، عَنْ مِقْسَمٍ، عَنْ أُمِّ سَلَمَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُوتِرُ بِخَمْسٍ وَبِسَبْعٍ لاَ يَفْصِلُ بَيْنَهَا بِسَلاَمٍ وَلاَ بِكَلاَمٍ ‏.‏
Grade :  Sahih (Darussalam)
Reference : Sunan an-Nasa'i 1714
In-book reference : Book 20, Hadith 117
English translation : Vol. 2, Book 20, Hadith 1715