Having examined the nature of Christ's presence in the Lord's Supper, the Roman Catholic understanding of the sacrament, and other matters, the Heidelberg Catechism, in questions and answers 81 and 82, discusses those who should be admitted to the Lord's Supper. Scripture deals with this issue in several passages, warning us that eating and drinking at the Lord's Table in an unworthy manner is great sin. It can even result in our deaths (1 Cor. 11:27–30).
What does it mean to partake of the Lord's Supper unworthily, and how can we avoid this error? These questions are not difficult to answer as long as we remember one fundamental principle: the Lord's Supper is not for sinless people. Sinless people do not need the Lord's Supper or the atonement it commemorates. Jesus instituted the sacrament at the Last Supper, giving it to His disciples, who were sinful men (Luke 22:14–20). Furthermore, Paul gave instructions on the sacrament to the Corinthian church, which was by no means perfect (1 Cor. 11:17–34). Finally, we will struggle with sin until we die or until Jesus returns, whichever comes first (1 John 1:8–9). Therefore, this sacrament cannot be for sinless people, since it is to be enjoyed regularly until Christ's return (1 Cor. 11:26).
Although the Lord's Supper is for sinners, it is not for impenitent sinners. Paul addresses this in today's passage when he says that we cannot partake of the Lord's Table and the table of demons (10:21). In this text, the Apostle addresses Corinthian believers who were participating in some of the meals that were a part of pagan worship. Buying meat in the marketplace left over from pagan sacrifices, which was permissible for the Corinthians (v. 25), was one thing, but engaging in the worship of pagan idols was another. This was a flagrant sin if there ever were one, and continued participation would have demonstrated a failure to trust Christ fully and no willingness at all to turn from sin.
Today, few of us are tempted to take part in pagan worship. We are all tempted, however, to sin with abandon and to remain stubborn and unrepentant. We are all tempted to worship the idols of our pleasures, and if we do so impenitently, we cannot be worthy partakers of the Lord's Supper.
In ourselves, we are all unworthy to approach the throne of grace because of our sin. To say we are worthy of taking the Lord's Supper is not to deny this fundamental reality; rather, it is to embrace it. For those worthy of taking part in the sacrament are those who have confessed their unworthiness before God, repented of their sin, and trusted in Christ alone for salvation. As we do this, we may come to His table for grace and strength.