In all three scenes recorded in the Gospel of Matthew the Gospel of Mark (probably the dictated Gospel of Peter) and the Gospel of Luke. Jesus calls the contents of the cup Wine, never His blood but wine. He stated clearly that the wine in the cup was to be drunk in remembrance of the blood of the new covenant to be shed for them the next day on the cross, and the fourth cup was poured out. Jesus Himself when Instituting the REMEMBRANCE used the WINE as the symbol of His blood shed for them and for us. At the actual instituting of the REMEMBRANCE the Lord Himself called the contents of the cup wine.
It would not be out of line to say that Jesus, knowing what trouble the disciples and which they held as questions from the months walking with Him, would clarify something as significant as John 6. For His friends, His closest followers who were, as best they could, 'down for the struggle'. He used the PAssove meal to institute the new covenant He was going to seal with His blood the next day, and He made clear the Truth of the bread and wine discourse from John 6 by passing among them pieces of bread He instructed to be eaten as a remembrance of His body about to be offered up BY HIM on the Cross for them. And he passed the cups of wine among them instructing all of them to drink from them because that wine in those cups, those Passover remembrance cups of wine, THAT wine was the symbol of His blood about to be shed for them.
Sitting at Passover table with His Disciples Jesus OUR HIGH PRIEST would not have violated the Levitical laws the night before His sealing the new covenant with His own Perfect and Righteous, full of His Life blood.
Folks can make alkl the fables up they want to, but the scene in John 6, as dartuser has stated so concisely, was not the establishment of the REMEMBRANCE COMMUNION! It may be what catholics point to as the establishment of catholic Eucharist, but that connects their ritual immediately tot eh curse upon any who drink blood, as clearly and unequivocally commanded BY GOD in Leviticus 3 and 17. The wine was made the symbol of His blood shed for us and He even said He would not drink WINE again until He drank it with them again in His Father's Kingdom. Read the Gospel passages for yourself. What is given in John 6 is not the establishment of THE REMEBRANCE. Jesus occasionally used sarcasm to address hardened hearts. He used that same technique with the hard hearts and those who He knew would not be all in for the mission.
BUT THE LORD did clarify in the John 6 scene, for those who remained, those who declared they were sticking with Him because He had the WORDS of eternal life. To them He clarified:
John 6:61And Jesus having known in himself that his disciples are murmuring about this, said to them, ‘Doth this stumble you? 62if then ye may behold the Son of Man going up where he was before? 63the spirit it is that is giving life; the flesh doth not profit anything; the sayings that I speak to you are spirit, and they are life; 64but there are certain of you who do not believe;’ for Jesus had known from the beginning who they are who are not believing, and who is he who will deliver him up, 65and he said, ‘Because of this I have said to you — No one is able to come unto me, if it may not have been given him from my Father.’66 From this [time] many of his disciples went away backward, and were no more walking with him, 67 Jesus, therefore, said to the twelve, ‘Do ye also wish to go away?’ 68 Simon Peter, therefore, answered him, ‘Sir, unto whom shall we go? thou hast sayings of life age-during; 69 and we have believed, and we have known, that thou art the Christ, the Son of the living God.’ [Young's Literal Translation]
Then the Jews began to argue sharply among themselves, "How can this man give us his flesh to eat?
That is not the reaction to a metaphor. This is the stark, amazed, horrified reaction to Christ's command that His disciples must eat His Body and drink His Blood.
Many of His disciples could not bear this hard teaching. They demurred: but Christ stood by His words. He did not retract or clarify them.
And then they left Him, unable to reconcile themselves to His stark and obvious meaning. Again, why would they do that if the command to eat His Body and drink His Blood was mere metaphor?
Right or wrong, they believed that Christ wasn't speaking in metaphor. His teaching shocked them into leaving. They could not accept it.
Do you believe that Christ was somehow hinting at metaphor?
If that were true, why then did so many disciples leave? Did Christ just not do a very good job of explaining His meaning?
Let's look at His words. Remember that He responds to the stark unbelief of his audience not once but twice.
Christ said this to the disciples:
I am the living bread that came down from heaven. Whoever eats this bread will live forever. This bread is my flesh, which I will give for the life of the world.”
And the Jews argued among themselves saying:
“How can this man give us his flesh to eat?”
Then Jesus said to them
Very truly I tell you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you.
Whoever eats my flesh and drinks my blood has eternal life, and I will raise them up at the last day. For my flesh is real food and my blood is real drink.
Does that sound like metaphor? For my flesh is real food and my blood is real drink?
Carrying on to the second statement of unbelief:
On hearing it, many of his disciples said,
This is a hard teaching. Who can accept it?
Aware that his disciples were grumbling about this, Jesus said to them,
Does this offend you? Then what if you see the Son of Man ascend to where he was before! The Spirit gives life; the flesh counts for nothing. The words that I have spoken unto you, they are Spirit, and they are Life
Christ backs up His words by saying that they are Spirit and they are Life.
At this point his audience could only have understood that Christ was standing behind his earlier words. Jesus made no changes to His words, no clarifications - because none were needed.
Are you saying that his faithful disciples were able to parse Christ's words - realizing that when He stated that His words were 'Spirit and Life' and that "His flesh was real food and His blood was real drink" that this meant that they didn't have to take them seriously?
But the unfaithful disciples left - because why? Because they didn't understand that He was speaking metaphorically? Did Christ let them walk away without explaining His meaning?
I hope that this is not what you believe. That would be insane. Christ is not some kind of divine Clinton whose words are not supposed to be taken literally, especially when He most insists on them.
Christ stood by His words. He declared them to be Spirit and Life. He declared that His flesh was real food and His blood was real drink.
No-one who heard Him was in any doubt that He meant what He said. His disciples left Him because He wasn't speaking metaphorically.
There are simply no other ways to take the John 6 narrative. Like those people in Capernaum we must accept that Christ literally means for us to eat His Flesh and drink His Blood.
And again - how could it be possibly against the Levitical law for Christ to perfectly fulfill the Passover? Christ is the Passover Lamb.
He is what all those centuries of Passovers and sacrifice were all about - they reached towards His Death and His Resurrection - His Living Sacrifice - at the center of all history.