The general sense of the verses under consideration is this. Do not murmur. Your murmuring will clarify nothing for you. The truth remains unshaken in the highest degree.
That truth is that I am the bread of life for you and for the whole world. This is such bread that the wondrous manna in the wilderness, which you recall, cannot be compared with it.
Your fathers ate that wondrous bread in the wilderness and nevertheless died. The wondrous character of that bread did not prevent their death.
But he who eats the bread of which I speak will never die, but will live forever.
"He who believes in Me," and so forth: see the note on Jn 6:40 and the parallels. "I am the bread of life": see the note on Jn 6:35.
"Your fathers ate the manna." The Jews themselves had earlier pointed to the wondrous manna, wishing to see a similar miracle from Jesus (Jn 6:31).
The Lord points to this and explains that the bread of which He speaks is more wondrous than manna and surpasses it in its action upon man.
This is shown by the fact that those who ate manna in the wilderness died, whereas the one who eats this bread will not die.
Death here means both bodily and spiritual death, but in different applications.
Those who ate manna in the wilderness all died bodily. Those also died spiritually who saw in that food only bodily food and did not abide in faith.
Those who partake of Christ's bread will die bodily, but they will be alive spiritually in communion with God through faith.
Then they will rise on the last day (Jn 6:39-40, 44) and will live forever in blessed life, in union with God.
But those who do not have such communion with God through partaking of this bread will, even after rising, remain in spiritual death.
They will remain in alienation from God, as those condemned (Jn 5:29).
"I am the living bread." The expressions "living bread" and "bread of life" differ from one another.
The first denotes life as a property of the bread itself. The latter denotes life as the effect produced by it in the one who partakes.
This effect, of course, depends on the fact that the bread itself has such a property. Therefore these expressions complete one another.
They ate manna in the wilderness and died, because manna was not living bread. The one who eats Christ's bread will not die, because this bread is living.
"And the bread is My Flesh," and so forth. Here is the essential supplement to the former discourse about bread, given by a particular explanatory feature.
The Lord suddenly resolves His enigmatic discourse by this feature, which completely astonished His hearers (Jn 6:52).
Until now, under the image of bread, He had spoken generally about His Person as the object of faith.
Now He speaks clearly, precisely, and definitively. The bread of which I speak is My Flesh.
"Here He speaks clearly of the mystical communion of His body" (Theophylact).
Flesh is the same as body, the bodily composition of the God-man. Here the word must be understood in a strictly literal sense, since there is no reason to understand it figuratively.
The word bread in this whole discourse plainly has a figurative or non-literal meaning, since it denotes here the Person of Christ in general.
By the word Flesh, a precisely determinative and concrete meaning is given to it.
The word manna, which concretely defines the general concept of the bread that once fed the Hebrews in the wilderness, plainly has a literal and direct meaning.
So too does the word Flesh, which defines the general meaning of bread.
"Note that the bread which we partake of in the mystery is not an image of the Lord's body, but is the very Flesh of the Lord.
For He did not say that the bread which I will give is an image of My flesh, but, 'is My Flesh'" (Theophylact).
"Which I will give for the life of the world." This is figurative speech about the Messiah's sacrifice on the Cross.
The Lord's Flesh was offered by Him on the Cross as a true sacrifice to God for the redemption of the sins of the whole world.
So too the typological sacrifice for sin under the law of Moses cleansed the sin of the one who offered it.
Since this sacrifice of the Cross on Golgotha was still ahead, the Lord speaks of it in the future tense: "I will give."
"For the life of the world" means so that the world may live, spiritually alive in union with God, who has been reconciled by this sacrifice.
The means for attaining this life is faith in the redemptive death of the Messiah, the God-man.
By the power of this faith the whole world would have received this life if the whole world had believed.
For Christ offered the redemptive sacrifice for all, for the whole world, and for the life of the whole world.
Until then the world had been alienated from God, and therefore in spiritual death because of sin.
For that sin, the reconciling sacrifice had not yet been offered by the Son of God.
Here one already clearly sees the Lord's reference to the paschal lamb, which His hearers were soon to eat at the approaching feast of Pascha (Jn 6:4).
In the following section (Jn 6:53 and following), this reference is still clearer and more decisive.
The Lord teaches about Himself as the true paschal lamb, who takes upon Himself the sins of the whole world.
The paschal lamb was only a type of this Lamb.
Before Pascha, the Lord was now giving His hearers to understand that the time of types is passing away and the truth itself is coming.
The eating of the paschal lamb will be replaced by the eating of Christ's body, offered in sacrifice for the sins of the whole world.
How this discourse of the Lord affected His hearers is seen from what follows.