Sahih al-Bukhari 991

Arabic

وَعَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يُسَلِّمُ بَيْنَ الرَّكْعَةِ وَالرَّكْعَتَيْنِ فِي الْوِتْرِ، حَتَّى يَأْمُرَ بِبَعْضِ حَاجَتِهِ‏.‏

Translation

Nafi` told that `Abdullah bin `Umar used to say Taslim between (the first) two Rak`at and (the third) odd one in the Witr prayer, when he wanted to attend to a certain matter (during that interval between the Rak`at)

Authenticity

Sahih

Reference