Hadith 502740
Chapter 7: Tahajjud - كتاب صلاة الليل
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يُسَلِّمُ بَيْنَ الرَّكْعَتَيْنِ وَالرَّكْعَةِ فِي الْوِتْرِ حَتَّى يَأْمُرَ بِبَعْضِ حَاجَتِهِ .
Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to say the taslim between the two rakas and the one raka of witr so that he could order something he needed.
Reference Muwatta Malik 502740
USC-MSA web (English) reference : Book 7, Hadith 20