Muwatta
Malik
موطأ مالك
07
Tahajjud
كتاب صلاة الليل
Chapter 3: The Command to Pray the Witr
Muwatta Malik 277
Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to say the taslim between the two Rak'ahs and the one Rak'ah of witr so that he could order something he needed.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يُسَلِّمُ بَيْنَ الرَّكْعَتَيْنِ وَالرَّكْعَةِ فِي الْوِتْرِ حَتَّى يَأْمُرَ بِبَعْضِ حَاجَتِهِ .