Sunan an-Nasa'i, Volume 2, Book 20, Hadith 1718 (DarusSalam) ⓘ
Hisham bin Urwah narrated from his father, from Aishah, that: The Prophet used to pray witr with five and he did not sit except in the last (rak'ah) of them.
أَخْبَرَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، قَالَ أَنْبَأَنَا عَبْدُ الرَّحْمَنِ، عَنْ سُفْيَانَ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ يُوتِرُ بِخَمْسٍ وَلاَ يَجْلِسُ إِلاَّ فِي آخِرِهِنَّ .
also referenced under: Hadith 1717 (Reference) & Book 20, Hadith 120 (In-Book)