What is the proper time frame for the Witr prayer?
Chapter on the Times When Prayer is Prohibited
Al-Mughni
Book of Prayer
Primary text
The time for the Witr prayer lies between the Isha prayer and the rising of the second dawn (Fajr). If Witr is performed before Isha, it is invalid. The time extends until the actual dawn breaks. Evidence for this timing includes the statement of the Prophet (peace be upon him): "Allah made Witr for you what is between the Isha prayer and the Fajr prayer." Furthermore, there is the hadith of Abu Basrah stating, "Allah has added an extra prayer for you; perform it between Isha and the morning prayer." In Al-Musnad, it is narrated from Mu'adh that he heard the Messenger of Allah (peace be upon him) say, "My Lord has granted me an additional prayer, which is Witr, and its time is between Isha and the breaking of dawn."
Supporting text
If Witr is delayed until the dawn breaks, its appointed time has passed, and it must be performed as a makeup prayer (Qada').