The present study does not propose an exhaustive approach to the way in which the Fathers understood the mission of the Church. We will stop at only three Fathers whom we considered representative of the subject in question and who are similar in many respects in the way they approach the problem of mission. It is very important that the common red thread that connects these three is the awareness that the external mission cannot be done without the internal adherence to the truth of the Gospel and to the life of the Church as it has always been understood. He who preaches to others must himself be a convert, but not in the simple and degraded sense of the term. Deep conversion to the word of the Gospel is the source that determines all pastoral and missionary success. Not the empty words, not the content of faith based exclusively on reason, but the inner coherence itself is what gives true content to any Orthodox missionary endeavor.