It is the sin against the Holy Spirit, because by not believing, one ignores the wooing of the Holy Spirit, thereby sinning against him.
LOYU W: Saytaane day wëtt ci xol wudd la amWattu ko bul ko wacc muy war di ku lëm Dafay woreek a weddilooy werentelooDi wàjji ngëm di wonni pas-pas du welu Wor ko te wodd xol bi ngëm...