11 And first, as regards the unity of the Christian faith, St. Cyril's untiring energy and unyielding tenacity in guarding it are well known. We (he writes) , to whom the truth and the doctrines of truth are most dear, refuse to follow these (heretics); we, taking the faith of the holy Fathers as our guide, will guard against all errors the divine revelation committed to our trust.
Source: Orientalis Ecclesiae (Vatican.va)