Sa'd bin Hisham narrates from Sayyidah Aishah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) did not say the salam in the two rak'ahs of the witr.
(b) Aban narrates from Qatadah that he used to pray three witr and sat in the last rak'ah.
The narration of Abd al-Wahhab appears to be an abridgement of the hadith, and the narration of Aban is a mistake.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4814