What did Jesus mean when He said we must "eat His flesh and drink His blood"?

Jesus was speaking about the spiritual world, not about the physical.

When He spoke of Himself as the Bread of Life, He was not speaking of bread that we eat with our mouths, but rather spiritual food which sustains our souls.

So when Jesus says "you must eat my flesh", He means that our souls need Him if we are to continue living after our physical bodies no longer function.

Jesus is the food and drink of our Spirit, He is our only true sustenance. The flesh counts for nothing, for we are spirit, not flesh.

Catholic understanding

Food noun

1. any nourishing substance that is eaten, drunk, or otherwise taken into the bbody to sustain life,provide energy, promote growth, etc.
2. more or less solid nourishment, as distinguished from liquids.
3. a particular kind of solid nourishment: a breakfast food; dog food.
4. whatever supplies nourishment to organisms: plant food.
5. anything serving for consumption or use: food for thought.

So when Jesus says For my flesh is food indeed, and my blood is drink indeed [cf. Jn 6:55], he really means that his flesh is food [for us] as we understand it. So there is living body and food that nourishes that body except in Holy Communion, there is a paradox, for while we are nourished,

"Ordinary food is consumed and becomes that which consumes it. In the Eucharist, we consume God and become that which we consume." cf. The Real Presence of Christ in the Eucharist: The Eucharist and Its Effects (2000-2012), James H. Dobbins, citing the work This Tremendous Lover (1989), by Dom Eugene Boylan.

The Body we are turned into is none other than to be in an ever increasing communion with the Church, which is the [Mystical] Body of Christ, His Bride:

The cup of blessing which we bless, is it not a participation [communion] in the blood of Christ? The bread which we break, is it not a participation in the body of Christ? [1 Cor 10: 16-17]

This brings us to 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 [cf. Jn 6:53]. That life in us is Christ’s own:

it is no longer I who live, but Christ who lives in me [cf. Gal 2:20]

Returning to the Church, the Body of Christ, being the Bride of Christ. Groom and Bride become one body [flesh] when they marry(cf. Gn 2:24 and Mt 19: 5-6).

Could this have been a reference to the Passover Lamb of which the Israelites were supposed to eat all of it? What is the common Protestant understanding of this? Do some traditions associate this with Communion?:

A. The symbolism is not opposed to the Catholic position but it is not its explanation.

Explanation from THE SACRED PASCHAL TRIDUUM (cf. Daily Roman Missal According to the Roman Missal, Third Edition)

THE MASS OF THE LORD'S SUPPER (HOLY THURSDAY)

At this supper on the night he was betrayed, the LORD Jesus, loving those who were his own in the world even to the end, offered his body and blood to the Father under the appearances of bread and wine, gave them to the apostles to eat and drink, then enjoined the apostles and their successors in the priesthood to offer them in return.

This Mass is, first of all, the memorial of the institution of the Eucharist, that is of the LORD's Passover, by which under sacramental signs he perpetuated among us the sacrifice of the New Law

CELEBRATION OF THE LORD'S PASSION (GOOD FRIDAY)

On this day when "Christ our Paschal Lamb was sacrificed" (1 Cor 5:7), what had long been promised in signs and figures was at last revealed and brought to fulfillment. The true lamb replaced the symbolic lamb, and many offerings of the past gave way to the single sacrifice of Christ.

Summary of the Catholic position: while the LORD is the true Paschal Lamb [of God] replacing the symbolic lamb of the LORD's Passover, his body (flesh) and blood that we eat and drink is not flesh and blood because of the symbolism with the Passover of the LORD's lamb, but actually his body and blood under the [appearances/] sacramental signs of [the consecrated] bread and wine.

Concluding, just as flesh the lamb of the LORD's Passover was eaten, the body of the true Paschal Lamb is to be eaten.The symbolism is not opposed to the Catholic position but it is not its explanation.

What did Jesus mean when He said we must “eat His flesh and drink His blood”?

John 6:53-54 (NASB)

53 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 yourselves. 54 He who eats My flesh and drinks My blood has eternal life...55 For My flesh is true food, and My blood is true drink.

It is recorded for us that Jesus Christ Himself gave the meaning of what he meant by His words through the immediate context of John 6:53-55. Before Jesus spoke these , he already said this:

John 6:35 (NASB)

35 Jesus said to them, “I am the bread of life; he who comes to Me will not hunger, and he who believes in Me will never thirst.

This shows that since the beginning of his discourse about the bread that comes down from heaven, Jesus never meant his words to be literal but only metaphorical.

To eat the flesh of Jesus means to come to Jesus.

To drink the blood of Jesus means to believe in Jesus.

What Jesus emphasizes on his words in the context of John 6:53-54 is His Incarnation not any bread and wine that change in substance (Transubstantiation).

John 6:26-65 (NASB)

26 Jesus answered them and said, “Truly, truly, I say to you, you seek Me, not because you saw signs, but because you ate of the loaves and were filled. 27 Do not work for the food which perishes, but for the food which endures to eternal life, which the Son of Man will give to you, for on Him the Father, God, has set His seal.” 28 Therefore they said to Him, “What shall we do, so that we may work the works of God?” 29 Jesus answered and said to them, “This is the work of God, that you believe in Him whom He has sent.” 30 So they said to Him, “What then do You do for a sign, so that we may see, and believe You? What work do You perform? 31 Our fathers ate the manna in the wilderness; as it is written, ‘He gave them bread out of heaven to eat.’” 32 Jesus then said to them, “Truly, truly, I say to you, it is not Moses who has given you the bread out of heaven, but it is My Father who gives you the true bread out of heaven. 33 For the bread of God is [i]that which comes down out of heaven, and gives life to the world.” 34 Then they said to Him, “Lord, always give us this bread.” 35 Jesus said to them, “I am the bread of life; he who comes to Me will not hunger, and he who believes in Me will never thirst. 36 But I said to you that you have seen Me, and yet do not believe. 37 All that the Father gives Me will come to Me, and the one who comes to Me I will certainly not cast out. 38 For I have come down from heaven, not to do My own will, but the will of Him who sent Me. 39 This is the will of Him who sent Me, that of all that He has given Me I lose nothing, but raise it up on the last day. 40 For this is the will of My Father, that everyone who beholds the Son and believes in Him will have eternal life, and I Myself will raise him up on the last day.” 41 Therefore the Jews were grumbling about Him, because He said, “I am the bread that came down out of heaven.” 42 They were saying, “Is not this Jesus, the son of Joseph, whose father and mother we know? How does He now say, ‘I have come down out of heaven’?” 43 Jesus answered and said to them, “Do not grumble among yourselves. 44 No one can come to Me unless the Father who sent Me draws him; and I will raise him up on the last day. 45 It is written in the prophets, ‘And they shall all be taught of God.’ Everyone who has heard and learned from the Father, comes to Me. 46 Not that anyone has seen the Father, except the One who is from God; He has seen the Father. 47 Truly, truly, I say to you, he who believes has eternal life. 48 I am the bread of life. 49 Your fathers ate the manna in the wilderness, and they died. 50 This is the bread which comes down out of heaven, so that one may eat of it and not die. 51 I am the living bread that came down out of heaven; if anyone eats of this bread, he will live forever; and the bread also which I will give for the life of the world is My flesh.” 52 Then the Jews began to argue with one another, saying, “How can this man give us His flesh to eat?” 53 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 yourselves. 54 He who eats My flesh and drinks My blood has eternal life, and I will raise him up on the last day. 55 For My flesh is true food, and My blood is true drink. 56 He who eats My flesh and drinks My blood abides in Me, and I in him. 57 As the living Father sent Me, and I live because of the Father, so he who eats Me, he also will live because of Me. 58 This is the bread which came down out of heaven; not as the fathers ate and died; he who eats this bread will live forever.” 59 These things He said in the synagogue as He taught in Capernaum. 60 Therefore many of His disciples, when they heard this said, “This is a difficult statement; who can listen to it?” 61 But Jesus, conscious that His disciples grumbled at this, said to them, “Does this cause you to stumble? 62 What then if you see the Son of Man ascending to where He was before? 63 It is the Spirit who gives life; the flesh profits nothing; the words that I have spoken to you are spirit and are life. 64 But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who it was that would [j]betray Him. 65 And He was saying, “For this reason I have said to you, that no one can come to Me unless it has been granted him from the Father.”

In the Bread of Life Discourse in John chapter 6, Jesus said:

John 6:35 Belief in Jesus = eternal life

John 6:36 Belief in Jesus = eternal life

John 6:40 Belief in Jesus = eternal life

John 6:47 Belief in Jesus = eternal life

John 6:64 Belief in Jesus = eternal life

John 6:54 eat the flesh and drink the blood of Jesus = eternal life

John 6:55 eat the flesh and drink the blood of Jesus = eternal life

John 6:59 eat the flesh and drink the blood of Jesus = eternal life

Was Jesus teaching about TWO WAYS to have eternal life?

1) Belief in Him

2) Eat his flesh and drink his blood

Of course not! John 6:35 is clear that to believe in Jesus is equivalent to eat Jesus [and will never be hungry] and to come to Jesus is equivalent to drink Jesus [and will never get thirsty].This shows that eating and drinking Jesus' flesh and blood by faith is a one time event or else, are we to believe [if it is literal] that we need to re-eat and re-drink Jesus' flesh and blood? This would contradict Jesus' words that we will never get hungry or thirsty if literal consumption was meant in John 6:35.

What did Jesus mean when He said that we must eat His Flesh and drink His Blood? Jesus meant that we must eat His Flesh and drink His Blood.

Jesus' followers said "This is a hard saying." Many of them left because they could not believe it was possible and Jesus did not call them back to say He did not mean that they were to eat His Flesh and drink His Blood. He asked His disciples if they were going to leave too because they did not believe Him. However, Peter answered, "Where else can we go? You have the Words of Eternal Life." Thereby signifying that they believed exactly what Jesus said.

They came to experience eating Jesus Flesh and drinking His Blood when Jesus served them Communion at "His Passover" (not The Passover of the Jews). Jesus Blessed the bread and broke it and told them, "Take and eat This is My Body..." and blessed the wine saying, "Take and drink, This is My Blood..." As His Disciples ate of the bread, believing it was Christ's Body and drank of the wine, believing it was Christ's Blood, then instead of just digesting bread and wine which would become a part of their body; Christ's Body and Blood assimilated them and they became a part of Christ's Body. They became Flesh of His Flesh and Bone of His Bone. They were then, by God's Grace and the Power of The Holy Spirit, able to fulfill their part of the continuing Ministry of Jesus Christ in this world.

If any follower of Christ goes to the Lords Table believing that the bread which they eat is Christ's Body and the wine that they drink is Christ's Blood, then Jesus' Body and Blood will make them a Member of Christ's Body, His Church. Then Jesus will always be with them to help them, heal them, provide for their needs, Love them, and give them the Peace of God which passes all understanding.

In Eastern Orthodoxy these verses are often read (if other hymns do not supplant or if the verses are not readily available) during the time communicants are coming up and receiving communion. It is also a part of many communion prayers verbatim. We are meant to understand they refer to the Eucharist itself.

Protestants usually say these are not literal but refer to the bread and wine he offers them before his betrayal only, and not to his actual flesh and blood.