"Now as they were eating, Jesus took bread, and after blessing it broke it and gave it to the disciples, and said, 'Take, eat; this is my body.' And he took a cup, and when he had given thanks he gave it to them, saying, 'Drink of it, all of you, for this is my blood of the covenant, which is poured out for many for the forgiveness of sins.'" - Matthew 26:26-28
"And as they were eating, He took bread, and after blessing it broke it and gave it to them, and said, 'Take; this is My body.' And He took a cup, and when He had given thanks He gave it to them, and they al drank of it. And He said to them, 'This is M blood of the covenant, which is poured out for many." - Mark 14:22-24
"And He took a cup, and when He had given thanks He said, 'Take this, and divide it among yourselves. For I tell you that from now on I will not drink of the fruit of the vine until the kingdom of God comes.' And he took bread, and when He had given thanks, he broke it and gave it to them, saying, 'This is my body, which is given for you. Do this in remembrance of Me.' And likewise the cup after they had eaten, saying, 'This cup that is poured out for you is the new covenant in My blood.'" - Luke 22:17-20
"So Jesus said to them, 'Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in you. Whoever feeds on My flesh and drinks My blood has eternal life, and I will raise Him up on the last day. For My flesh is true food, and My blood is true drink. Whoever feeds on My flesh and drinks My blood abides in Me, and I in him.'" - John 6:53-56
"I speak as to sensible people; judge for yourselves what I say. The cup of blessing that we bless, is it not partaking in the blood of Christ? The bread that we break, is it not partaking of the body of Christ? Because there is one bread, we who are many are one body, for we all partake of the one bread. Consider the people of Israel: are not those who eat the sacrifices partakers of the altar?" - 1 Corinthians 10:15-18
"For I received from the Lord what I also delivered to you, that the Lord Jesus on the night when He was betrayed took bread, and when He had given thanks, He broke it, and said, 'This is My body, whic his for you. Do this in remembrance of Me.' In the same way also He took the cup, after supper, saying, 'This cup is the new covenant in My blood. Do this, as often as you drink, in remembrance of Me.' For as often as you eat this bread and drink the cup, you proclaim the Lord's death until He comes.
Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty concerning the body and blood of the Lord. Let a person examine himself, then, and so eat of the bread and drink of the cup. For a nyone who eats and drinks without discerning the body eats and drinks judgment on himself." - 1 Corinthians 11:23-29
And from the testimony of the ancient fathers:
"They [heretics] abstain from the Eucharist and from prayer, because they do not confess the Eucharist to be the flesh of our Savior Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again." - Ignatius of Antioch, Epistle to the Smyrnaeans, Ch. 7, c. 107 AD
"And this food is called among us Eucharist, of which no one is allowed to partake but the one that believes the things which we teach are true, and who has been washed with the washing that is for the forgiveness 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 Savior, 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 change 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, 'Do this 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, Ch. 66, c. 150 AD
"He took that created thing, bread, and gave thanks, and said, 'This is My body.' And the cup likewise, which is part of that creation to which we belong, He confessed to be His blood, and taught the new oblation of the New Covenant; which the Church receiving from the apostles, offers to God throughout all the world," - Irenaeus of Lyons, Against Heresies Book IV, 17.5, c. 180 AD
"But in vain in every respect are those who despise the entire dispensation of God, and disallow the salvation of the flesh, and treat with contempt its regeneration, maintaining that it is not capable of incorruption. But if this indeed does not attain salvation, then neither did the Lord redeem us with His blood, nor is the cup of the Eucharist the partaking of His blood, nor the bread which we break the partaking of His body. For blood can only come from veins and flesh, and whatsoever else makes up the substance of man, such as the Word of God was actually made. By His own blood He redeemed us, as also His apostle declares, 'In whom we have redemption through His blood, even the remission of sins.' And as we are His members, we are also nourished by means of the creation (and He Himself grants the creation to us, for He causes His sun to rise, and sends rain when He wills). He has acknowledged the cup (which is part of the creation) as His own blood, and which He bedews our blood; and the bread (also a part of the creation) He has established as His own body, from which He gives increase to our bodies.
When, therefore, the mixed cup and the manufactured bread receives the word of God, and the Eucharist of the blood and body of Christ is made, from which things the substance of our flesh is increased and supported, how can they affirm that the flesh is incapable of receiving the gift of God, which is life eternal, which [flesh] is nourished from the body and blood of the Lord, and is a member of Him?--even as the blessed Paul declares in his Epistle to the Ephesians, that 'we are members of His body, of His flesh, and of His bones.' He does not speak these words of some spiritual and invisible man, for a spirit has not bones nor flesh; but [he refers to] that dispensation [by which the Lord became] an actual man, consisting of flesh, and nerves, and bones" - ibid. Book V, 2.2-3
-CryptoLuthera