Sayyiduna Nu'man bin Bashir (may Allah be pleased with him) narrates: I said: O Messenger of Allah, what do you recite in the witr? The Prophet (peace and blessings be upon him) said: Surah al-A'la, Surah al-Kafirun and Surah al-Ikhlas.
Imam al-Tabarani recorded this narration in al-Mu'jam al-Awsat; its chain contains a narrator, al-Sari bin Isma'il, who is extremely da'if (weak).