It is Jesus’ words in the discourse that are also gift to the crowds along with the bread. The words are the gateway for the ones who ate the bread to see and believe (6:40) and thus to have life and live forever (6:51, 58). At the same time, one must eat the bread in order to live (6:53, 58). These are part of the seamless union of flesh, spirit, humanity, and divinity that are part of the integrity of the whole of Chapter 6.
It seems to me that too many commentators separate the miraculous feeding (vv.1-25) from the Christological and theological content of what follows. Their comparison point is no longer the Johannine miraculous feeding but rather the synoptic Eucharistic institution, norms of the primitive church and later patristic periods, and developing theology of later ages up and through the 17th century.
John’s narrative uses the metaphor of bread to pave the foundation of the whole of the chapter. The phrase “bread from heaven” intentionally points to the events of the Exodus (Ex 16) and the manna – the locus of God’s faithfulness and the people’s grumbling. At the same time it points to the language and image of Isaiah 55, “why spend your money for what is not bread, your wages on what fails to satisfy?” There the bread from heaven represents the Word of God that gives and sustains life. Thus in the one metaphor of bread, John draws upon two different gifts from God: the gifts of that which sustains the flesh and that which sustains the Spirit – but not in ways that are apart and separate – but in the wholeness of the human person. There is no gnostic undertone within John that raises the Spirit above the flesh with the end-game of leaving “useless flesh” behind.
Jesus draws upon these metaphors and transforms them in himself as the one to whom the OT metaphors point, as the context in which the fullness of “I am the bread of life” is to be understood. Jesus is the “living bread come down from heaven,” the food that gives life – not the manna of the wilderness or the multiplied loaves. It is through eating Jesus’ flesh and drinking his blood that the believer shares in this food. Jesus is the bread that people must eat to have life (6:53-56) and he is also the bread to whom one must listen in order to have life (6:45, 63, 68). It is the same trajectory of Jesus’ offer of new life to Nicodemus and the living water offered to the Samaritan woman at the well. There are many avenues to God, all passing through Jesus.
The institution of the Eucharist is rightly placed and well described by the synoptic gospels, but the Eucharist does not belong solely or uniquely to the death of Jesus (v.51), rather the Johannine Eucharist points to the whole of Jesus’ life and “marks the believer’s full participation in all of Jesus’ life and gifts.” (O’Day, 613). That full participation, body and soul, is the manner is which one “abides” in Jesus. One abides in the Word and in the breaking of the bread – and in so doing receives life through Jesus’ abiding presence. There is no divide between faith and action, Word and Eucharist, body and soul. For the Fourth Evangelist, the Eucharist belongs to and is inseparable from the revelation of God in Jesus. “At the heart of both word and sacrament is the urgency for people to see God in Jesus and believe.” (O’Day 614)