Eternal sin
In Christian hamartiology, eternal sins, unforgivable sins, or unpardonable sins are sins which will not be forgiven by God. One eternal or unforgivable sin (blasphemy against the Holy Spirit) is specified in several passages of the Synoptic Gospels, including , , and .
Blasphemy
Blasphemy has been condemned as a serious sin by the major creeds and Church theologians (apostasy and infidelity [unbelief] were generally considered to be the gravest sins, with heresy a greater sin than blasphemy, cf. Thomas Aquinas' "Summa Theologiae").