When the Prayer begins during Tawaf
Question:
What is the ruling if the prayer starts and the Hajj pilgrim or the Umrah pilgrim has not completed Tawaf or Sa'y?
Answer:
He prays with the people and then he completes his Tawaf or Sa'y from where he left off. He begins from wherever he stopped.
Source:
Shaykh `Abdul-`Azeez Bin Baz
Fatawa Islamiyah Darussalam Vol:4 page no.182