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.
Christian views on sin
The first reference to "sin" as a noun is of ""sin" is crouching at your door; it desires to have you, but you must rule over it” waiting to be mastered by Cain, a form of literary theriomorphism. 
The first use of the verb is God appears to Abimelech "in the dream, “Yes, I know you did this with a clear conscience, and so I have kept you from "sinning" against me. That is why I did not let you touch her.”" in Genesis 20:3. Isaiah announced the consequences: "But your iniquities have separated you from your God; your sins have hidden his face from you, so that he will not hear. For your hands are stained with blood, your fingers with guilt. Your lips have spoken falsely, and your tongue mutters wicked things" — a separation between God and man, and unrequited worshipping.