The first altar to be built to the worship of God since Noah (Genesis 8:20) was after the call of Abram when the Lord said to him, “‘To your offspring I will give this land.'” So, “[Abram] built there an altar to the LORD, who had appeared to him” (Genesis 12:7). Why did Abram build the altar? Because of two symbiotic reasons: the Lord appeared to him and gave him a promise. This origin of the altar provides deeper meaning to our Gottesdienst, that is, Divine Service. Remember, O reader mine, that we call it “Divine Service” because of what is occurring: heaven and earth meet and God appears to us in His divine service of Word and Sacrament and gives us His promises therein. Therefore, when the pastor invokes the name of the Triune God at the altar, God is present there. When you approach the Sacrament of the Altar, Christ is truly present there in His body and blood.
Christ has made this quite evident not only when He instituted the Lord’s Supper by saying “This is My body, this is My blood” (Matthew 26:26-28), but also in the Bread of Life discourse in the Gospel of John. “I AM the bread of life. Your fathers ate the manna in the desert, and they died. This is the bread that comes down from Heaven, so that one may eat of Him and not die. I AM the living bread that came down from Heaven. If anyone eats of this bread, he will live forever; and also, the bread that I Myself will give on behalf of the life of the world is My flesh” (John 6:48-51; my translation).
There has been a lot of debate about whether Jesus is speaking of a spiritual eating of His flesh (faith in what He did on the cross) or a literal eating of His flesh in the Lord’s Supper. I am of the opinion that it is both, not either/or. For what do we Lutherans say about the Supper’s relation to the cross? We say the Supper is the receiving of what He accomplished on the cross. This is the best way to read John 6. Yes, He is most immediately speaking of a “spiritual eating” of His flesh by faith in what He is going to accomplish on the cross, and He is also speaking of a literal eating to receive its benefits. The early church interpreted it both ways as well.
The following dialogue makes this most convincing, “Then the Jews began to quarrel with one another, saying, ‘How can this man give us His flesh to eat?’ Therefore, Jesus said to them, ‘Truly, truly, I say to you, if you do not eat the flesh of the Son of Man and drink His blood, you do not have life in yourselves. He who eats My flesh and drinks My blood has life eternal, and I Myself will raise him up on the last day” (vv. 52-54; my translation). Jesus doubles down on His literalism; He does not explain that He was speaking figuratively, as He’s done at other times. It makes little sense that Jesus is only speaking of a spiritual eating when He makes mention of the manna the Israelites ate, which was not a spiritual eating but a literal eating.
This is all to make the point that Christ makes Himself present at the altar to give us His promise of eternal life, which He accomplished for us in His flesh and blood on the cross. The only way to receive this promise is by faith, yes (John 3:16), and also the literal eating of His body and blood just as He promised. “But Luther says we are saved by faith alone,” one might say, as if that means Christ’s doesn’t use His Sacraments as the means by which He gives faith and saves. Yes, faith alone saves, and faith alone receives the promises given in the Sacraments, just as we confess, “Who receives this sacrament worthily? Fasting and bodily preparation are certainly fine outward training. But that person is truly worthy and well prepared who has faith in these words, ‘Given and shed for you for the forgiveness of sins‘” (SC, The Sacrament of the Altar). Just as Abraham, by faith, “went to live in the land of promise” (Hebrews 11:9), so by faith we approach Christ at the altar to receive the promise of forgiveness of sins, eternal life, and salvation.