St. Mark, the disciple and interpreter of St. Peter (saith St. Jerome), according to what he heard from Peter himself, wrote at Rome a brief Gospel at the request of the Brethren, about ten years after our lord's Ascension; which when Peter had heard, he approved of it and with his authority published it to the church to be read. Baronius and others say that the original was written in Latin: but the more general opinion is that the Evangelist wrote it in Greek.
