Reference: Siyar A’laam an-Nubalaa – Volume 8, Page 540
Ahmad al-’Ajalee said:
Ishaaq al-Fazaaree – a man of Sunnah – was the one who disciplined the people of ath-Thughar and taught them the Sunnah. And if an innovator entered ath-Thughar, he would oust him [to protect the people of ath-Thughar from his innovation].
