In the first place, the mass is a denial of the one finished sacrifice of Jesus Christ. At the basis of this whole Romish conception of the Lord’s Supper and the mass lies their error of transubstantiation. That false doctrine leads to these other errors. According to their conception, at the word of the priest in consecrating the elements, those signs of bread and wine are changed into the physical body and blood of Christ. Therefore Christ is there, again physically, to be offered as a sacrifice for sins. And that sacrifice is essential unto salvation. So essential is it, that Rome has priests. That is why Rome speaks not of the communion table, as do we when we speak of this table, even of the table of the covenant, as I referred to it in connection with Lord’s Day 28; but Rome speaks of the altar. Rome calls its people to the altar. And through the church, that is, through the priest, Christ is offered even continually as a sacrifice for the sins of the people. That is necessary, according to Rome.
Now, don’t be deceived by them. If you were to ask a member of the Romish clergy, “Do you believe that Christ alone saves His people,” he will say, “Sure; of course.” If you were to ask him, “Do you believe that the sacrifice of Christ on the cross is sufficient for the atonement of sins,” he will answer, “We most certainly do.” That is why you have to listen to the complete explanation which they give. They say and teach emphatically, even in their official confessions, that unless the sacrifice of Christ is repeatedly offered in the mass, the atonement of Christ cannot be applied to the sinner. And therefore for you, for the people of God, even for the dead, to receive the forgiveness of sins, it is necessary that the priest repeatedly offer Christ in an unbloody sacrifice in the mass. There only do you have the application of the forgiveness of sins. The mass is said for the living and for the dead, for those who come to the altar to receive the host, and for those that are in purgatory. That is the repeated sacrifice of Christ offered in Roman Catholicism.
In the second place, the mass is called by our Heidelberg Catechism “an accursed idolatry.” That is strong language indeed. The Roman Catholic Church will most ardently deny this. Of course. And you can understand even how they can deny this. If you grant that in the words of consecration the elements are changed—not spiritually, but physically into the body and blood of Christ; if you grant that, then you have Christ, the physical Christ before you on the altar. Then, of course, you may worship him. That is why, until they have seen the error of transubstantiation, they cannot possibly see their idolatry. But idolatry is exactly what it is. For they worship not Christ, but the signs.