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 seven or five rak'ahs, and would not separate them with a salam or with speech.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20197