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:
Ten Commandments
In Gospel of Barnabas, Jesus stated that idolatry is the greatest sin as it divests a man fully of faith, and hence of God. In his time, Idolatry is not only worshipping statues of wood or stone; but also statues of flesh. All which a man loves, for which he leaves everything else but that, is his god, thus the glutton and drunkard has for his idol his own flesh, the fornicator has for his idol the harlot and the greedy has for his idol silver and gold, and so the same for every other sinner.