References, from as early as 80 AD, to the Real Presence of Christ in the Eucharist, From http://www.therealpresence.org/eucharst/father/a5.html:
The Didache or “The Teaching of the Twelve Apostles” is a manuscript which was used by 2nd century bishops and priests for the instruction of catechumens. Many early Christian writers have referenced it making this document relatively easy to date.
“Let no one eat and drink of your Eucharist but those baptized in the name of the Lord; to this, too the saying of the Lord is applicable: ‘Do not give to dogs what is sacred'”.
“On the Lord’s own day, assemble in common to break bread and offer thanks; but first confess your sins, so that your sacrifice may be pure. However, no one quarreling with his brother may join your meeting until they are reconciled; your sacrifice must not be defiled. For here we have the saying of the Lord: ‘In every place and time offer me a pure sacrifice; for I am a mighty King, says the Lord; and my name spreads terror among the nations.'”
ST. CLEMENT OF ROME (Alt)
St. Clement was the third successor of Peter as Bishop of Rome; otherwise known as the third Pope.
“Since then these things are manifest to us, and we have looked into the depths of the divine knowledge, we ought to do in order all things which the Master commanded us to perform at appointed times. He commanded us to celebrate sacrifices and services, and that it should not be thoughtlessly or disorderly, but at fixed times and hours. He has Himself fixed by His supreme will the places and persons whom He desires for these celebrations, in order that all things may be done piously according to His good pleasure, and be acceptable to His will. So then those who offer their oblations at the appointed seasons are acceptable and blessed, but they follow the laws of the Master and do not sin. For to the high priest his proper ministrations are allotted, and to the priests the proper place has been appointed, and on Levites their proper services have been imposed. The layman is bound by the ordinances for the laity.”
Source: St. Clement, bishop of Rome, 80 A.D., to the Corinthians
“Our sin will not be small if we eject from the episcopate those who blamelessly and holily have offered its Sacrifices.”
Source: Letter to the Corinthians, [44,4]
ST. IGNATIUS OF ANTIOCH (Alt)
St. Ignatius became the third bishop of Antioch, succeeding St. Evodius, who was the immediate successor of St. Peter. He heard St. John preach when he was a boy and knew St. Polycarp, Bishop of Smyrna. Seven of his letters written to various Christian communities have been preserved. Eventually, he received the martyr’s crown as he was thrown to wild beasts in the arena.
“Consider how contrary to the mind of God are the heterodox in regard to the grace of God which has come to us. They have no regard for charity, none for the widow, the orphan, the oppressed, none for the man in prison, the hungry or the thirsty. They abstain from the Eucharist and from prayer, because they do not admit that the Eucharist is the flesh of our Savior Jesus Christ, the flesh which suffered for our sins and which the Father, in His graciousness, raised from the dead.”
“Letter to the Smyrnaeans”, paragraph 6. circa 80-110 A.D.
“Come together in common, one and all without exception in charity, in one faith and in one Jesus Christ, who is of the race of David according to the flesh, the son of man, and the Son of God, so that with undivided mind you may obey the bishop and the priests, and break one Bread which is the medicine of immortality and the antidote against death, enabling us to live forever in Jesus Christ.”
-“Letter to the Ephesians”, paragraph 20, c. 80-110 A.D.
“I have no taste for the food that perishes nor for the pleasures of this life. I want the Bread of God which is the Flesh of Christ, who was the seed of David; and for drink I desire His Blood which is love that cannot be destroyed.”
-“Letter to the Romans”, paragraph 7, circa 80-110 A.D.
“Take care, then who belong to God and to Jesus Christ – they are with the bishop. And those who repent and come to the unity of the Church – they too shall be of God, and will be living according to Jesus Christ. Do not err, my brethren: if anyone follow a schismatic, he will not inherit the Kingdom of God. If any man walk about with strange doctrine, he cannot lie down with the passion. Take care, then, to use one Eucharist, so that whatever you do, you do according to God: for there is one Flesh of our Lord Jesus Christ, and one cup in the union of His Blood; one altar, as there is one bishop with the presbytery and my fellow servants, the deacons.”
-Epistle to the Philadelphians, 3:2-4:1, 110 A.D.
ST. JUSTIN MARTYR (Alt)
St. Justin Martyr was born a pagan but converted to Christianity after studying philosophy. He was a prolific writer and many Church scholars consider him the greatest apologist or defender of the faith from the 2nd century. He was beheaded with six of his companions some time between 163 and 167 A.D.
“This food we call the Eucharist, of which no one is allowed to partake except one who believes that the things we teach are true, and has received the washing for forgiveness of sins and for rebirth, and who lives as Christ handed down to us. For we do not receive these things as common bread or common drink; but as Jesus Christ our Savior being incarnate by God’s Word took flesh and blood for our salvation, so also we have been taught that the food consecrated by the Word of prayer which comes from him, from which our flesh and blood are nourished by transformation, is the flesh and blood of that incarnate Jesus.”
“First Apology”, Ch. 66, inter A.D. 148-155.
“God has therefore announced in advance that all the sacrifices offered in His name, which Jesus Christ offered, that is, in the Eucharist of the Bread and of the Chalice, which are offered by us Christians in every part of the world, are pleasing to Him.”
“Dialogue with Trypho”, Ch. 117, circa 130-160 A.D.
Moreover, as I said before, concerning the sacrifices which you at that time offered, God speaks through Malachias, one of the twelve, as follows: ‘I have no pleasure in you, says the Lord; and I will not accept your sacrifices from your hands; for from the rising of the sun until its setting, my name has been glorified among the gentiles; and in every place incense is offered to my name, and a clean offering: for great is my name among the gentiles, says the Lord; but you profane it.’ It is of the sacrifices offered to Him in every place by us, the gentiles, that is, of the Bread of the Eucharist and likewise of the cup of the Eucharist, that He speaks at that time; and He says that we glorify His name, while you profane it.”
-“Dialogue with Trypho”, [41: 8-10]
ST. IRENAEUS OF LYONS (Alt)
St. Irenaeus succeeded St. Pothinus to become the second bishop of Lyons in 177 A.D. Earlier in his life he studied under St. Polycarp. Considered, one of the greatest theologians of the 2nd century, St. Irenaeus is best known for refuting the Gnostic heresies.
[Christ] has declared the cup, a part of creation, to be his own Blood, from which he causes our blood to flow; and the bread, a part of creation, he has established as his own Body, from which he gives increase to our bodies.”
Source: St. Irenaeus of Lyons, Against Heresies, 180 A.D.:
“So then, if the mixed cup and the manufactured bread receive the Word of God and become the Eucharist, that is to say, the Blood and Body of Christ, which fortify and build up the substance of our flesh, how can these people claim that the flesh is incapable of receiving God’s gift of eternal life, when it is nourished by Christ’s Blood and Body and is His member? As the blessed apostle says in his letter to the Ephesians, ‘For we are members of His Body, of His flesh and of His bones’ (Eph. 5:30). He is not talking about some kind of ‘spiritual’ and ‘invisible’ man, ‘for a spirit does not have flesh an bones’ (Lk. 24:39). No, he is talking of the organism possessed by a real human being, composed of flesh and nerves and bones. It is this which is nourished by the cup which is His Blood, and is fortified by the bread which is His Body. The stem of the vine takes root in the earth and eventually bears fruit, and ‘the grain of wheat falls into the earth’ (Jn. 12:24), dissolves, rises again, multiplied by the all-containing Spirit of God, and finally after skilled processing, is put to human use. These two then receive the Word of God and become the Eucharist, which is the Body and Blood of Christ.”
-“Five Books on the Unmasking and Refutation of the Falsely
Named Gnosis”. Book 5:2, 2-3, circa 180 A.D. “For just as the bread which comes from the earth, having received the invocation of God, is no longer ordinary bread, but the Eucharist, consisting of two realities, earthly and heavenly, so our bodies, having received the Eucharist, are no longer corruptible, because they have the hope of the resurrection.”
-“Five Books on the Unmasking and Refutation of the Falsely named Gnosis”. Book 4:18 4-5, circa 180 A.D.