Thomas Aquinas

“ Thus then it is not necessary for salvation to confess one's faith at all times and in all places, but in certain places and at certain times, when, namely, by omitting to do so, we would deprive God of due honor, or our neighbor of a service that we ought to render him: for instance, if a man, on being asked about his faith, were to remain silent, so as to make people believe either that he is without faith, or that the faith is false, or so as to turn others away from the faith; for in such cases as these, confession of faith is necessary for salvation. ”

“ Hence it is written (Mat. 15:12) that when the disciples had said to Our Lord that "the Pharisee, when they heard this word, were scandalized," He answered: "Let them alone, they are blind, and leaders of the blind." ”

“ In cases of necessity where faith is in danger, every one is bound to proclaim his faith to others, either to give good example and encouragement to the rest of the faithful, or to check the attacks of unbelievers: but at other times it is not the duty of all the faithful to instruct others in the faith. ”