And Nafi' narrates that
Hazrat Abdullah bin Umar (Allāh be pleased with them both) used to say the salam between the one rak'ah of Witr and the two rak'ahs, to the extent that he would give an instruction for some need of his.
وَعَنْ نَافِعٍ
أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَانَ يُسَلِّمُ بَيْنَ الرَّكعةِ وَالرَّكْعَتَيْنِ فِي الوِتْرِ حَتَّى يَأْمُر بِبَعْضِ حَاجَتِهِ
Reference: Sahih Al Bukhari 991