What is the ruling on performing Witr after Fajr time has begun?

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If a person wakes up having missed the Witr prayer before dawn, the Witr rak'ah is not established unless one fears the rising of the sun. If one intends to pray Witr after Fajr has commenced, one should pray three rak'ahs, which includes establishing two rak'ahs before the Witr, unless the rising of the sun is imminent.