Heidelberg Catechism, Lord’s Day 29
Q78. Do the bread and wine become
the real body and blood of Christ?
Just as the water of baptism
is not changed into Christ’s blood
and does not itself wash away sins
but is simply a divine sign and assurance of these things,
so too the holy bread of the Lord’s Supper
does not become the actual body of Christ,
even though it is called the body of Christ
in keeping with the nature and language of sacraments.
Q79. Why then does Christ call
the bread his body
and the cup his blood,
or the new covenant in his blood,
and Paul use the words,
a sharing in Christ’s body and blood?
A79. Christ has good reason for these words.
He wants to teach us that
just as bread and wine nourish the temporal life,
so too his crucified body and poured-out blood
are the true food and drink of our souls for eternal life.
But more important,
he wants to assure us, by this visible sign and pledge,
that we, through the Holy Spirit’s work,
share in his true body and blood
as surely as our mouths
receive these holy signs in his remembrance,
and that all of his suffering and obedience
are as definitely ours
as if we personally
had suffered and made satisfaction for our sins.