Matthew 12:31
30 Whoever is not with me is against me, and whoever does not gather with me scatters. 31 For this reason I tell you, people will be forgiven for every sin and blasphemy, but the blasphemy against the Spirit will not be forgiven. 32 Whoever speaks a word against the Son of Man will be forgiven. But whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.
Yoma 86a
Babylonian TalmudThese are the categories: If one violates a positive mitzva and repents, he is forgiven even before he moves from his place, i.e. immediately, as it is stated: “Return, you backsliding children, I will heal your backsliding” (Jeremiah 3:22), implying that when one repents he is immediately forgiven. If one violates a prohibition and repents, repentance suspends his punishment and Yom Kippur atones for his sin, as it is stated: “For on this day shall atonement be made for you, to purify you from all your sins” (Leviticus 16:30). If one commits a transgression that warrants karet or a sin punishable by death from the earthly court and then repents, repentance and Yom Kippur suspend his punishment, and suffering absolves and completes the atonement, as it is stated: “Then will I visit their transgression with the rod, and their iniquity with strokes” (Psalms 89:33). But in the case of one who has caused desecration of God’s name, his repentance has no power to suspend punishment, nor does Yom Kippur have power to atone for his sin, nor does suffering alone have power to absolve him. Rather, all these suspend punishment, and death absolves him, as it is stated: “And the Lord of Hosts revealed Himself to my ears: This iniquity shall not be atoned for until you die” (Isaiah 22:14).
Notes and References
"... Desecration of the Holy Name is a graver sin than any other (Jerusalem Nedarim 38b; Sanhedrin 107a): it is an iniquity which. according to Isaiah 22:14 (Yoma 86a) - shall never be expiated until death - a tradition strangely altered into the New Testament ('Blasphemy against the Holy Ghost shall not be forgiven unto men') Matthew 12:31 and parallels. The desire to sanctify the name of God. on the other hand, leads men to treat adherents of other creeds with the utmost fairness and equity ..."
Singer, Isidore The Jewish Encyclopedia: A Descriptive Record of the History, Religion, Literature, and Customs of the Jewish People from the Earliest Times to the Present Day (Volume 5) (p. 250) Funk & Wagnalls, 1912