This meal is a sacrament. But what is a sacrament? Where does this use come from? The answer to that question—given the nature of what we are doing here—cannot be confined to one simple answer, but it does have an answer.
The use of the Latin word sacramentum was introduced by the early father Tertullian, who took it from the oath of allegiance that a Roman soldier would swear upon enlistment. This element is certainly present—at the sacrament of baptism, the one baptized is being bound by oath to serve Christ for the rest of his or her life. Every time we take the sacrament of the bread and wine, we are again swearing our allegiance to Christ. But there is more to it.
The word sacramentum came to be the word used to translate the Greek word mysterion. What to the Greeks were mysteries were to the Romans sacraments. Augustine took Tertullian’s concept and developed it further, and defined a sacrament as an outward and visible sign of an interior and invisible grace. The oath is objective; the person is bound whether or not he meant it when he made it. But the oath includes the assumption that the profession is sincere. When it is not sincere, when the outward and visible sign does not line up with a heart-felt desire to follow Jesus Christ, then the sacrament is being defiled.
Note that the sacrament is not a nullity. Unbelief cannot undo God’s Word. It is the other way around. God’s Word is what undoes unbelief, destroying the hypocrisy, either by judging it or converting it. Abuse of the Supper was why many of the Corinthians were sick and dying. Their sin could not make the Supper get sick and die. Christ already died, and has risen to everlasting life. Death cannot touch Him, which is the central point, is it not?
So come, and welcome, to Jesus Christ.