Abu Dawud Book 2, Hadith Number 1419.
Chapter : What is recited in the witr.
Narated By ‘Aisha, Ummul Mu’minin : Abdul Aziz ibn Jurayj said: I asked ‘Aisha, mother of the believers: With which (surah) the Apostle of Allah (PBUH) used to observe witr? (She reported same as in the Hadith of Ubayy ibn Ka’b, No. 1418)
This version adds: In the third rak’ah he would recite: “Say, He is Allah, the One” (Surah 112), and “Say, I seek refuge in the Lord of daybreak” (Surah 113), and “Say, I seek refuge in the Lord of mankind” (Surah 114).