What does John 6:50 mean?

Jesus has been explaining how "bread that comes down from heaven" is not literal bread. Rather, it is a person (John 6:33), whose message is meant to bring people into eternal life (John 6:27–29), so long as they believe in the One sent by God. The miraculous manna which Israel received in the wilderness (Exodus 16) and the bread which Jesus created on the prior day (John 6:11–15) were only meant to be signs, or symbols, pointing towards a greater, eternal truth.

The manna which Israel ate in the wilderness was symbolic of Jesus. Manna was small, white, round, and arrived at night. These are symbols of humility, purity, eternity, and times of spiritual darkness, respectively. It could not be made or transferred; it had to be individually accepted. Manna was also found on the ground, leaving only two options: receive it as a gift or walk right over it (John 3:16–18).

Jesus' statement that "this is the bread that comes down from heaven" has two purposes. First, it emphasizes that Jesus is explaining the true meaning and the true purpose behind the symbol of bread. Secondly, Jesus is explicitly referring to Himself (John 6:51) as the fulfillment of this idea. In the wilderness, God sent a source of physical life from heaven in the form of bread. Now, God has sent the source of eternal life from heaven in the form of Jesus Christ.

To this point, Jesus has pointed out the need for belief in the One sent by God. This is controversial enough and has caused the people to grumble under their breath (John 6:41). In the next verse, however, Jesus will expand the symbolic meaning of "bread." He does this by equating the "bread of life" to His own flesh: symbolic of His upcoming death on the cross. This analogy will be immediately misinterpreted and the crowd will become even angrier.