Mattityahu 12:31-32

Therefore, I say to you, every chet (sin) and gidduf (blasphemy) will be forgiven men, but whoever commits Chillul HASHEM against the Ruach Hakodesh will not be forgiven. And whoever speaks a word against the Bar Enosh will be granted selicha (forgiveness), but whoever speaks against the Ruach Hakodesh, selicha will not be granted him either in the Olam Hazeh or in the Olam Habah.