Eternal sin
In Catholic teaching there are six sins that blaspheme against the Holy Spirit. They are: Several passages in the Bible are frequently interpreted as referring to the unforgivable sin:
Sacrament of Penance
Practically all writings of that period, for instance "The Shepherd of Hermas", "Didache" or "Letters of St. Ignace of Antioch", show that grave sins were not rare among Christians. Cyrille Vogel collected a list of twelve major sins named in the New Testament and the Apostolic Fathers' writings. They are all various transgressions of the Ten Commandments: