Reference: Fataawa al-Hajj wal-‘Umrah waz-Ziyaarah – Page 80
Question: What is the ruling about the one performing the Hajj or the ‘Umrah and when the obligatory prayer begins, he has not finished the tawaaf or sa’ee?
Response: He should pray with the congregation, then continue his tawaaf or sa’ee from where he had stopped [just before the prayer]. So he starts from where he stopped.