Jesus introduced a new metaphor for believing on Him, namely eating His flesh. The following pericope is highly metaphorical.
6:52 As Jesus' hearers had objected to what He had said about His identity (vv. 41-42), so they now expressed confusion about what He meant by eating flesh. An intense argument (Gr. emachonto) erupted among them. They were struggling to understand His meaning. In what sense would Jesus give His flesh as food?
6:53-54 This is the fourth and last of Jesus' strong prefaces in this discourse (cf. vv. 26, 32, 47). It should be obvious to any readers of this discourse by now that Jesus was speaking metaphorically and not literally. By referring to His flesh and blood He was figuratively referring to His whole person. This is a figure of speech called synecdoche in which one part stands for the whole. Jesus was illustrating belief, what it means to appropriate Him by faith (v. 40). He expressed the same truth negatively (v. 53) and then positively (v. 54a). He referred again to resurrection because it is the inauguration of immortal eternal life (cf. vv. 39, 40, 44).
Jesus was again stressing His identity as the revealer of God with the title "Son of Man."Blood in the Old Testament represented violent death primarily. Thus Jesus was hinting that He would die violently. He connected the importance of belief in Him with His atoning death. The idea of eating blood was repulsive to the Jews (cf. Lev. 3:17; 17:10-14). Jesus' hearers should have understood that He was speaking metaphorically, but this reference offended many of them (vv. 60-61).
Many interpreters of these verses have seen allusions to the Lord's Supper in what Jesus said. Sacramentalists among them find support here for their belief that participation in the eucharist is essential for salvation. However, Jesus had not yet said anything about the Christian communion service. Moreover He was clearly speaking of belief metaphorically, not the communion elements. Most important, the New Testament presents the Lord's Supper as a commemoration of Jesus' death, not a vehicle for obtaining eternal life. Nevertheless these verses help us appreciate the symbolism of the eucharist.
"In short, John 6 does not directly speak of the eucharist; it does expose the true meaning of the Lord's supper as clearly as any passage in Scripture."261
6:55 This verse explains why Jesus' statements in verses 53 and 54 are true. Jesus' person is what truly satisfies and sustains life. This is the true function of food and drink.
6:56 Because Jesus' person is what truly satisfies and sustains life those who believe in Him remain (Gr. meno, abide) in Him. This is a new term in the discussion, but it is synonymous with having eternal life. Jesus was saying that believers continue to possess eternal life; they will never lose it. Believers remain in Christ, and He remains in them. Jesus was not speaking here to His disciples about the importance of believers abiding in fellowship with God as He did in chapter 15. Here He was speaking to unbelievers about entering into a saving relationship with God.
6:57 Jesus traced the eternal life that the believer receives when he or she trusts in Jesus back through the Son to the living God (cf. 5:21, 24-27). This helps us see that eternal life is essentially God's life that He imparts to believers. It also clarifies Jesus' central role as the mediator of eternal life from the Father to humankind.
6:58 In conclusion, Jesus returned to His initial claim that He had come from the Father (v. 29). The Jews often substituted the term "heaven"for "God"out of respect for God's name, and Jesus did that here.262The Israelites who ate the physical bread that came down from God died in the wilderness (vv. 30-31), but those who believe in the spiritual Bread that came down from Him will live forever.
6:59 John now identified the historical context in which Jesus gave this teaching. Jesus gave this discourse in the synagogue in the town that He had adopted as the headquarters of His ministry (cf. 2:12). This verse evidently marks the conclusion of the discussion that took place within the synagogue. What followed probably happened outside the building or at least after Jesus had concluded His discourse.
Archaeologists have uncovered what they believe may be the foundations of this synagogue. Visitors to the town may now view a reconstructed edifice that dates from three or four hundred years later.
The Apostle Paul went to the Jewish synagogues in the towns that he evangelized because they were the places where pious Jews normally congregated to listen to God's Word. We should probably view Jesus' teaching ministry here as similar to Paul's later practice. Both men announced God's revelations to lost religious Jews and appealed to them to believe the gospel.