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 ye in remembrance of Me, 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.
— Justin Martyr. First Apology LXVI. ANF01
And the offering of fine flour, … which was prescribed to be presented on behalf of those purified from leprosy, was a type of the bread of the Eucharist, the celebration of which our Lord Jesus Christ prescribed, in remembrance of the suffering which He endured on behalf of those who are purified in soul from all iniquity, in order that we may at the same time thank God for having created the world, with all things therein, for the sake of man, and for delivering us from the evil in which we were, and for utterly overthrowing principalities and powers by Him who suffered according to His will.
— Justin Martyr. Dialogue with Trypho XLI. ANF01
Accordingly, God, anticipating all the sacrifices which we offer through this name, and which Jesus the Christ enjoined us to offer, i.e., in the Eucharist of the bread and the cup, and which are presented by Christians in all places throughout the world, bears witness that they are well-pleasing to Him. But He utterly rejects those presented by you and by those priests of yours, saying, ‘And I will not accept your sacrifices at your hands; for from the rising of the sun to its setting my name is glorified among the Gentiles, but ye profane it.’ … Prayers and giving of thanks, when offered by worthy men, are the only perfect and well-pleasing sacrifices to God. For such alone Christians have undertaken to offer, and in the remembrance effected by their solid and liquid food, whereby the suffering of the Son of God which He endured is brought to mind.
— Justin Martyr. Dialogue with Trypho CXVII. ANF01