It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) would pray witr with five or seven rak'ahs, and he would not separate them with any speech or with a salam.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19921