It is reported about Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that he would come out when Ibn al-Tayyah gave the call to prayer at the first dawn, and Sayyiduna Ali (may Allah be pleased with him) would say: This is the best hour for the witr. He said this interpreting this verse of the Qur'an (Allah Almighty says): "And by the dawn when it breathes."
Imam al-Tabarani recorded this narration in al-Mu'jam al-Awsat; its chain contains a narrator, al-Hasan bin Abi Ja'far al-Jafri, who is matruk (abandoned).