God is an all forgiving Father. The Bible says in Isaiah 1: 18 that though our sins be as scarlet or red like crimson, they shall be as white as snow, implying that no matter how terrible our sins are God is faithful and just to forgive us and cleanse us from all unrighteosness. As to the extent of forgiveness, Other places like Ps 103 vs 12, Mic 7:19, Is 38:17, is 43:25 Ps 51:1,9, Jer 31:34 makes it clear that God not only forgives but forgets our sins and remembers them no more. However in Matt 12vs 31 and 32, Jesus made this statement;
" Wherefore I say unto you, all manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men. And whosoever speaketh a word against the son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall not be forgiven him, neither in this World, neither in the World to come."
Now how do we harmonize these or better still what exactly is this Sin against the Holy spirit?