"Interviewer: You often say that more than a question of liturgy, today it is a question of faith that opposes us to the current Rome. Mgr. Lefebvre: Of course, the question of liturgy and the sacraments is very important, but it is not the most important. The most important question is that of faith. For us, it is settled. We have the faith of always, that of the Council of Trent, of the Catechism of Saint Pius X, of all the Councils and of all the Popes before Vatican II."
January 1, 1970
https://en.wikiquote.org/wiki/Marcel_Lefebvre