According to Sacred Scripture, precisely baptism's unrepeatability — makes it the one and only life-long sacrament. By grace and through faith alone, it indeed signifies the forgiveness of all sins — past, present, and future. For baptism needs no augmentation with endless post-baptismal repeated applications of 'holy water' (like a whole series of pseudo-rebaptisms). Nor does baptism need augmentation by Rome's pseudo-sacraments of confirmation, the mass, penance, ordination (or alternatively marriage), and extreme unction.
Calvin's response to Trent on the 'seven sacraments'
Now Trent finished setting forth the Romish doctrine of baptism at that Seventh Session — on 3rd March, 1547.18 Calvin then responded — in his Antidote to Trent — on 21st November, 1547.19
Trent alleged:20 "Whosoever shall say that the Sacraments…are either more or fewer than seven (namely Baptism, Confirmation, the Eucharist, Penance, Extreme Unction, [Holy] Orders and Matrimony) — or even that any one of these seven is not truly and properly a Sacrament — let him be anathema!… Whosoever shall say that these seven Sacraments are so equal among themselves that no one is in any respect of greater dignity than another — let him be anathema!"
To this, we see Calvin respond21 in 1547 that in the Sacred Scriptures "we read that baptism was recommended by Christ. We read in like manner that the Lord's supper was recommended…. Of the others [the Romanists’ remaining five quasi-sacraments], we read nothing of the kind…..
"Not contented, however, with claiming equal authority for all — they prefer the chrism of their confirmation to the baptism of Christ. For their making one of more dignity than another, is not for the purpose of placing those which have no support from Scripture in an inferior grade. But they renew those execrable blasphemies which the Council of Aurelium first vented — that we are made only 'Half-Christian' by baptism, and are finished by confirmation."
Here, Rome implies that baptism is indeed unrepeatable — but that confirmation is more important that baptism. In his reply, Dr. Calvin too assumes the unrepeatability and indeed the life-long effectiveness of baptism. Confirmation, on the other hand, is to him no sacrament at all — and grossly inferior to life-long baptism.
Calvin responds to Trent on the ex opere operato
Trent continues:22 "Whosoever shall say that by these [seven] Sacraments…grace is not conferred ex opere operato (from the work performed), but that faith alone in the divine promise suffices to obtain grace — let him be anathema!"
Calvin here responds to the Romanists:23 "Here indeed they disclose their impiety not only more clearly but also more grossly. The device of opus operatum is recent [post-patristic], and was coined by illiterate monks who had never learned anything of the nature of sacraments….
"If we grant their postulate — that grace is procured in the sacraments opere operato — a part of merit is separated from faith, and the use of the sacraments is in itself effectual for salvation." However, "the apostle is a witness that they are of no avail, unless received by faith." See: Acts 8:12-23; First Corinthians 1:12-17; First Peter 3:20f ; compare Mark 16:16. Yet throughout, Dr. Calvin never
questions the validity of baptisms administered once and for all — even if so served within the Church of Rome.
Trent and Calvin on unrepeatable baptism's "indelibility"
Trent further alleges:24 "Whosoever shall say that in the three Sacraments — namely Baptism, Confirmation and [Holy] Orders — there is not impressed on the soul a character, i.e., some spiritual and indelible sign owing to which they cannot be repeated — let him be anathema!"