Heidelberg Catechism LD #30

Lord's Day 30

80. What difference is there between the Lord's Supper and the Pope's Mass?

The Lord's Supper testifies to us that we have full forgiveness of all our sins by the one sacrifice of Jesus Christ, which He Himself once accomplished on the cross; and that by the Holy Spirit we are engrafted into Christ, who, with His true body is now in heaven at the right hand of the Father, and is there to be worshiped. But the Mass teaches that the living and the dead do not have forgiveness of sins through the sufferings of Christ, unless Christ is still daily offered for them by the priests, and that Christ is bodily under the form of bread and wine, and is therefore to be worshiped in them. And thus the Mass at bottom is nothing else than a denial of the one sacrifice and suffering of Jesus Christ,5 and an accursed idolatry.

81. Who are to come to the table of the Lord?

Those who are displeased with themselves for their sins, yet trust that these are forgiven them, and that their remaining infirmity is covered by the suffering and death of Christ; who also desire more and more to strengthen their faith and to amend their life. But the unrepentant and hypocrites eat and drink judgment to themselves.

82. Are they, then, also to be admitted to this Supper who show themselves by their confession and life to be unbelieving and ungodly?

No, for thereby the covenant of God is profaned and His wrath provoked against the whole congregation;1 therefore, the Christian Church is bound, according to the order of Christ and His Apostles, to exclude such persons by the Office of the Keys until they amend their lives.