Some people have understood Jesus to be speaking literally, and they connect what he says here to the Lord’s Supper. They think that in the Lord’s Supper a miracle takes place and that the bread and wine of the of the communion table are literally changed into the body and blood of Christ. The technical term for this belief is transubstantiation.
But it seems clear to me that when Jesus spoke of our need to eat his flesh and drink his blood that he was using a very common Hebrew metaphor. We find this sort of thing in the Scriptures really quite often – where the idea of eating and drinking is used in a metaphorical sense.
For instance, we frequently find the Scriptures representing the weapons of war as eating the flesh and drinking the blood of those who are slain. The Lord uses this as an image of judgment.
“I will make my arrows drunk with blood, and my sword shall devour flesh” (Deut. 32:42)We find something similar in 2 Samuel, where we have an account of a battle between David and the forces of his son Absalom. It says, “The battle spread over the face of all the country, and the forest devoured more people that day than the sword” (2 Sam. 18:8). In other words, the forest killed more people than the sword did. You might remember that Absalom himself met his end by getting his hair caught in a tree (2 Sam. 18:9-15).
“That day is the day of the Lord God of hosts, a day of vengeance, to avenge himself on his foes. The sword shall devour and be sated and drink its fill of their blood” (Jer. 46:10)
There are a great many instances in Scripture of this kind of metaphorical use of eating and drinking. In the book of Job it is said that man “drinks injustice like water” (Job 15:16), meaning (in the first place) that man in his fallen state has a thirst for sin and (in the second place) fully partakes of it.
In Proverbs the evil man is said to “eat the bread of wickedness and drink the wine of violence” (Prov. 4:17), meaning that he hungers and thirsts for these things, and is filled with them. Solomon also says that “fools feed on folly” (Prov. 15:14).
The metaphor of eating and drinking is also often used in connection with assimilating knowledge of divine things and growing spiritually. Jeremiah says, “Your words were found and I ate them” (Jer. 15:16). Paul tells the Corinthians that he fed them with milk and not with solid food because they were not ready for it (1 Cor.3:1-2). Peter tells his readers to “long for the pure spiritual milk” (1 Pet. 2:2).
It seems clear to me that Jesus was using these terms in the same metaphorical sense when he says that we must eat his flesh and drink his blood.
When one eats and drinks, two things happen: 1.) hunger and thirst are satisfied, and 2.) whatever is consumed is assimilated into the person consuming it. People in the ancient world understood this. Perhaps they couldn’t give you a biological or scientific explanation of how it happened, but they understood that somehow, when food was taken into the body, it was transformed into the body – it somehow provided nourishment, health, and strength for the body.
When Jesus says that we must eat his body and drink his blood—and that unless we do so, we have no life in us—he means that we are to fully appropriate to ourselves all the saving benefits of his sacrificial death. I don’t think there can be any more powerful way of expressing this than by saying what Jesus said—that we eat his body, as it were, and that we drink his blood; that we consume him.
How do we do this? Well, we consume Christ by believing in him. Consuming the flesh and blood of Christ is equated with believing in him. In this same chapter the very same benefits are promised to believing in him as are promised to eating his flesh and drinking his blood (vv. 35, 40, 47).
There are several metaphors the Scriptures use for believing in Christ. They sometimes speak, for instance, of “looking to” Jesus (Jn. 6:40; 12:44-45); or of “knowing” him; but in my opinion, there is no more powerful description of believing—no more vivid portrayal of faith—than that of eating and drinking. To believe in Christ is to consume him. There is no such thing as a casual faith in Jesus. One’s faith in Christ, if it exists at all, is both passionate and consuming. Real faith in Christ is an aggressive thing. It lays a hold of him and makes him one’s own.