On our journey from the slavery of Egypt (a slavery broken by Baptism) to the Promised Land (i.e., to heaven), the Eucharist nourishes us, enabling us to live on the toilsome road from slavery under sin to freedom under grace. The Eucharist is that “Bread from heaven” that nourishes us and sustains us as the old manna sustained the Israelites on their journey through the desert into the Promised Land. In the discourse on the Bread of Life, Jesus himself establishes the parallel between Passover and the Eucharist, for the manna is associated with the “passing” from Egypt to the Promised Land. It is the bread of our journey, the new manna.
In John 6, Jesus emphasizes that his body must be eaten and his blood must be drunk. The Greek word he uses (John 6:50, 51, 52, 53; so too, in Mt) for “eat” is φάγειν (phagein), to eat up or devour. The word is not to be taken “metaphorically,” because “to eat someone’s flesh” is to act with hostility towards that person, as we see in Psalm 27:2 (in Hebrew, to eat up my flesh; in the Septuagint: phagein tas sarkas mou). Zechariah 11:9 offers a similar case. The Aramaic tradition is that the title of the devil is, “Eater of Flesh.” How, then, could Jesus have mean this metaphorically?
So, Catholics believe that just as the Paschal sacrifice was really to be eaten, so too Christ is really to be eaten. We are to partake of him by eating his flesh and drinking his blood (1 Cor 10:16–18). By drinking from this cup and eating this food, we “proclaim the Lord’s death until he comes” (1 Cor 11:26). This proclamation is a “remembrance” that has OT roots. It calls God’s attention to what he has done, urging that He apply His mercy concretely in the present. Obviously, when people in the OT (and now, when Catholics) try to get God to remember, they know full well that God is moving them to ask Him to remember. They know full well that He does not forget and that He does not change. However, God wants active involvement from us. That is why Scripture often uses anthropomorphic language when God is seeking human cooperation with his grace. He is seeking human involvement. One can think of God interacting with Adam in Gen 2, interacting with Abraham before condemning Sodom in Gen 18, and interacting with Moses in Ex 32.). What we are remembering, in the case of the Eucharist, is the real presence of Jesus, the substance of his flesh and soul, always united in person with his divinity.
Jesus even underscores the really physical character of Eucharistic eating. In John 6:54 he says, “He who eats my flesh and drinks my blood has eternal life.” For “he who eats,” John uses a participle meaning “to much on or gnaw” (ό τρώγων, from the verb τρώγειν). The verb was originally used with reference to animals chewing and grinding vegetables. Later, it was used for humans “chowing down” so to speak, as one might see in Matthew 24:38. John hereby records Jesus’ emphasis on the physicality of the Eucharist. (He even uses it again in what is the Johannine parallel to the Last Supper scene, John 13:18, “He who ate my bread has lifted his heel against me,” from Psalm 41:9).
Now, we might wonder—certainly, any 8 to 10 year old wonders—why on earth we should “eat the flesh” of a man. Since the beginning of Christianity, pagans, Jews, and even some “disciples” of Christ have wondered this very thing: “‘This is a hard saying; who can listen to it?’” (John 6:60). The saying was so difficult that some left Jesus: “After this many of his disciples drew back and no longer went about with him” (John 6:66). Apologists rightly use this reaction to the great teacher Jesus as an argument that he meant what he said. He was not pulling back when he added that “My words are spirit and life”.
But back to the larger question: Why this rite? One rationale behind this strange rite is that by eating, as Paul says, we participate in Christ’s life. To “participate” is to take part in, to have a heritage with. Through this rite, we “imbibe” Jesus and have his life in us. Since we want this life in us—for Jesus is the Way, the Truth, and the Life—we drink his blood and eat his flesh. Jesus himself says, in John 6:56, “He who eat my flesh and drinks my blood abides in me, and I in him.” Through this physical “sharing,” Jesus brings us to commune with him more and more, sustaining us in our journey to the Father. To “abide” in Jesus is to live in that love by which the Father first loved us through Jesus.
So, in the end there is a Trinitarian dimension to this great mystery: “As the living Father sent me, and I live because of the Father, so he who eats (ό τρώγων) me will live because of me.” Jesus receives everything from the Father (John 3:35). “For as the Father has life in himself, so he has granted the Son also to have life in himself…” John 5:26. In turn, Jesus passes on everything, what he is—Body, Blood, Soul, and Divinity—to us in the Eucharist
So we see the Trinitarian dimension: in receiving Jesus we are actually receiving one who receives from the Father all that he is; the one who is sent out to others. The Eucharist then increases our identification with Christ: we are those who receive everything as a gift from God; consequently, who are sent out to others, to serve all in the law of love. Jesus specifies this in John 15:9–13, where he urges us to abide in his love and the Father’s love by keeping the commandment of love.