Pope St. Sixtus III

“Let us at God's bidding rejoice in a good and pleasant thing, for once again we begin as "brethren to dwell together in unity". We wish your holiness to proclaim what you write. From the outcome of this affair you have learnt I what it means to be in agreement with us. he blessed apostle Peter, in his successors, has handed down what he received. Who would be willing to separate himself from the doctrine of him whom the Master himself instructed first among the apostles? It was not hearsay or selected speech which taught him; he was trained with the others by the mouth of the teacher. He had I not to search among writings and writers; he received the I original and direct faith which can admit of no dispute, on which we must always meditate, and in which we must abide, so that following the apostles with a pure affection, we may be counted apostolical.” (Epistle 6 [Si ecclesiastici], to John, Bishop of Antioch).