Who was Justin Martyr? The Catholic Encyclopedia states that he was a "Christian apologist, born at Flavia Neapolis, about A.D. 100, converted to Christianity about A.D. 130, taught and defended the Christian religion in Asia Minor and at Rome, where he suffered martyrdom about the year 165. Two `Apologies' bearing his name and his `Dialogue with the Jew Tryphon' have come down to us. Leo XIII had a Mass and an Office composed in his honour and set his feast for 14 April." From his First Apology, here is St. Justin Martyr on the Eucharist:
And this food is called among us Εὐχαριστία [the Eucharist], of which no one is allowed to partake but the man who believes that the things which we teach are true, and who has been washed with the washing that is for the remission of sins, and unto regeneration, and who is so living as Christ has enjoined. For not as common bread and common drink do we receive these; but in like manner as Jesus Christ our Saviour, having been made flesh by the Word of God, had both flesh and blood for our salvation, so likewise have we been taught that the food which is blessed by the prayer of His word, and from which our blood and flesh by transmutation are nourished, is the flesh and blood of that Jesus who was made flesh. For the apostles, in the memoirs composed by them, which are called Gospels, have thus delivered unto us what was enjoined upon them; that Jesus took bread, and when He had given thanks, said, This do in remembrance of Me, Luke 22:19 this is My body; and that, after the same manner, having taken the cup and given thanks, He said, This is My blood; and gave it to them alone. Which the wicked devils have imitated in the mysteries of Mithras, commanding the same thing to be done. For, that bread and a cup of water are placed with certain incantations in the mystic rites of one who is being initiated, you either know or can learn.