Musannaf Ibn Abi Shaybah

Hazrat Ali (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) used to perform Witr at the time of the Adhan, and used to perform two rak‘ahs at the time of Iqamah. In the narration of Hazrat Salam, there is this addition that he used to perform Witr at the time of the first Adhan. Hazrat Salam says that I heard Hazrat Abu Ishaq say that he (the Prophet) used to perform Witr at the time of the rising of Fajr.