It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to pray two rak'ahs seated after witr, in which he recited Surah al-Zalzalah and Surah al-Kafirun.
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 8034