New City Catechism 47.3
Question 47: Does the Lord's Supper add anything to Christ's atoning work? Answer: No, Christ died once for all. The Lord's Supper is a covenant meal celebrating Christ's atoning work; it is also a means of strengthening our faith as we look to him, and a foretaste of the future feast. But those who take part with unreprentant hearts eat and drink judgment on themselves. When churches specify who is and is not welcome to eat the Lord's Supper, this practice is called "fencing