This is my body ... This is my blood ...
Matthew 26:26-28
And as they were eating, Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take, eat; this is my body. And he took the cup, and gave thanks, and gave it to them, saying, Drink ye all of it; For this is my blood of the new testament, which is shed for many for the remission of sins.

Mark 14:22-24
And as they did eat, Jesus took bread, and blessed, and brake it, and gave to them, and said, Take, eat: this is my body. And he took the cup, and when he had given thanks, he gave it to them: and they all drank of it. And he said unto them, This is my blood of the new testament, which is shed for many.

Luke 22:19-20
And he took bread, and gave thanks, and brake it, and gave unto them, saying, This is my body which is given for you: this do in remembrance of me. Likewise also the cup after supper, saying, This cup is the new testament in my blood, which is shed for you.

1 Corinthians 11:24-25
And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me. After the same manner also he took the cup, when he had supped, saying, This cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.

Sinning against the body and blood.
1 Corinthians 11:26-30
For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come. Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord. But let a man examine himself, and so let him eat of that bread, and drink of that cup. For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord's body. For this cause many are weak and sickly among you, and many sleep.

Long discourse on Eucharist.
John 6:32-58
Then Jesus said unto them, "Verily, verily, I say unto you, Moses gave you not that bread from heaven; but my Father giveth you the true bread from heaven. For the bread of God is he which cometh down from heaven, and giveth life unto the world."

Then said they unto him, "Lord, evermore give us this bread."

And Jesus said unto them, "I am the bread of life: he that cometh to me shall never hunger; and he that believeth on me shall never thirst. But I said unto you, That ye also have seen me, and believe not. All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out. For I came down from heaven, not to do mine own will, but the will of him that sent me. And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day. And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day."

The Jews then murmured at him, because he said, "I am the bread which came down from heaven." And they said, "Is not this Jesus, the son of Joseph, whose father and mother we know? how is it then that he saith, I came down from heaven?"

Jesus therefore answered and said unto them, "Murmur not among yourselves. No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day. It is written in the prophets, 'And they shall be all taught of God.' Every man therefore that hath heard, and hath learned of the Father, cometh unto me. Not that any man hath seen the Father, save he which is of God, he hath seen the Father. Verily, verily, I say unto you, He that believeth on me hath everlasting life. I am that bread of life. Your fathers did eat manna in the wilderness, and are dead. This is the bread which cometh down from heaven, that a man may eat thereof, and not die. I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world."

The Jews therefore strove among themselves, saying, "How can this man give us his flesh to eat?"

Then Jesus said unto them, "Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you. Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day. For my flesh is meat indeed, and my blood is drink indeed. He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him. As the living Father hath sent me, and I live by the Father: so he that eateth me, even he shall live by me. This is that bread which came down from heaven: not as your fathers did eat manna, and are dead: he that eateth of this bread shall live for ever."

Melchizedek.
Genesis 14:18
And Melchizedek king of Salem brought forth bread and wine: and he was the priest of the most high God.

Psalm 110:4
The LORD hath sworn, and will not repent, "Thou art a priest for ever after the order of Melchizedek."

Hebrews 7:1-17
For this Melchisedec, king of Salem, priest of the most high God, who met Abraham returning from the slaughter of the kings, and blessed him; To whom also Abraham gave a tenth part of all; first being by interpretation "King of righteousness", and after that also King of Salem, which is, "King of peace"; Without father, without mother, without descent, having neither beginning of days, nor end of life; but made like unto the Son of God; abideth a priest continually.

Now consider how great this man was, unto whom even the patriarch Abraham gave the tenth of the spoils. And verily they that are of the sons of Levi, who receive the office of the priesthood, have a commandment to take tithes of the people according to the law, that is, of their brethren, though they come out of the loins of Abraham: But he whose descent is not counted from them received tithes of Abraham, and blessed him that had the promises. And without all contradiction the less is blessed of the better. And here men that die receive tithes; but there he receiveth them, of whom it is witnessed that he liveth. And as I may so say, Levi also, who receiveth tithes, payed tithes in Abraham. For he was yet in the loins of his father, when Melchisedec met him.

If therefore perfection were by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron? For the priesthood being changed, there is made of necessity a change also of the law. For he of whom these things are spoken pertaineth to another tribe, of which no man gave attendance at the altar. For it is evident that our Lord sprang out of Juda; of which tribe Moses spake nothing concerning priesthood.

And it is yet far more evident: for that after the similitude of Melchisedec there ariseth another priest, Who is made, not after the law of a carnal commandment, but after the power of an endless life. For he testifieth, "Thou art a priest for ever after the order of Melchisedec."

Breaking of bread.
Acts 2:42
And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers.

Symbolic interpretation of John 6 inappropriate
This is the case because, in the Bible, symbolically "eating someone's flesh" means "to revile" or "assault" someone, which doesn't make sense in the context of John 6. Therefore, John 6 must be interpreted literally, since Jesus couldn't have meant that to inherit eternal life, we would have to revile or assault Him. Below are some examples of the symbolic sense of "eating someone's flesh".

Psalm 27:1-2
The LORD is my light and my salvation; whom shall I fear? the LORD is the strength of my life; of whom shall I be afraid? When the wicked, even mine enemies and my foes, came upon me to eat up my flesh, they stumbled and fell.

Isaiah 9:18-21
For wickedness burneth as the fire: it shall devour the briers and thorns, and shall kindle in the thickets of the forest, and they shall mount up like the lifting up of smoke. Through the wrath of the LORD of hosts is the land darkened, and the people shall be as the fuel of the fire: no man shall spare his brother. And he shall snatch on the right hand, and be hungry; and he shall eat on the left hand, and they shall not be satisfied: they shall eat every man the flesh of his own arm: Manasseh, Ephraim; and Ephraim, Manasseh: and they together shall be against Judah. For all this his anger is not turned away, but his hand is stretched out still.

Isaiah 49:26
And I will feed them that oppress thee with their own flesh; and they shall be drunken with their own blood, as with sweet wine: and all flesh shall know that I the LORD am thy Saviour and thy Redeemer, the mighty One of Jacob.

Micah 3:3
Who also eat the flesh of my people, and flay their skin from off them; and they break their bones, and chop them in pieces, as for the pot, and as flesh within the caldron.

Revelation 17:6,16
And I saw the woman drunken with the blood of the saints, and with the blood of the martyrs of Jesus: and when I saw her, I wondered with great admiration.... And the ten horns which thou sawest upon the beast, these shall hate the whore, and shall make her desolate and naked, and shall eat her flesh, and burn her with fire.

A prophecy on the celebration of the Eucharist.
Malachi 1:10-11
Who is there even among you that would shut the doors for nought? neither do ye kindle fire on mine altar for nought. I have no pleasure in you, saith the Lord of hosts, neither will I accept an offering at your hand. For from the rising of the sun even unto the going down of the same my name shall be great among the Gentiles; and in every place incense shall be offered unto my name, and a pure offering: for my name shall be great among the heathen, saith the Lord of hosts.