Eternal sin
Thomas Aquinas lists, or has responded to, six sins that supposedly go against the Holy Spirit:
Thomas Aquinas explains that the unforgivability of blasphemy against the Holy Spirit means that it removes the entrance to these means of salvation; however, it cannot hinder God in taking away this obstacle by way of a miracle.
Islamic views on sin
This Quranic verse indicates that "khati’ah" is considered an "ithm", a grave sin. In fact, the word "khati’ah" is associated with some of the most heinous religious sins in the Quran. In one Quranic verse this word is used to describe the sin of slaying one's own children for fear of poverty. (Quran 17:33/31). Scholars believe that "dhanb" or "ithm" could be used in place of "khati’ah" in this instance; however, the word choice indicates that "khati’ah" is more than just a moral lapse or mistake and is punishable.