If the Athan for Fajr is called during Witr
Question:
A man was praying Witr and during his prayer, the Mu'aththin called the Athan for the Fajr prayer. What is the ruling, should he complete the prayer, or not?
Answer:
Yes, if the Athan was called while he was praying Witr, he should complete his prayer and there is no sin in that.
Shaykh Muhammad bin Saalih al-`Uthaymeen
Fatawa Islamiyah Vol. 2 Page 314
