Shevuot 13A

בעומד במרדו, ורבי היא. דתניא: רבי אומר, על כל עבירות שבתורה, בין עשה תשובה בין לא עשה תשובה ⁠– יום הכפורים מכפר; חוץ מפורק עול ומגלה פנים בתורה ומפר ברית בבשר ⁠– שאם עשה תשובה, יום הכפורים מכפר; ואם לאו, אין יום הכפורים מכפר.

The Mishnah is referring to a case where the person did not repent and persists in his rebellion, and it is in accordance with the opinion of R' Yehuda HaNasi, that even for such a case Yom Kippur and the scapegoat will atone. As it is taught in a baraita: R' Yehuda HaNasi says: For all transgressions that are stated in the Torah, whether one repented, or whether one did not repent, Yom Kippur atones, except for one who divests himself of the yoke of Heaven, by denying God’s existence, and one who reveals facets of the Torah that differ from its true meaning, and one who nullifies the covenant of circumcision of the flesh. For these, if one repented, Yom Kippur atones, and if not, Yom Kippur does not atone.

מאי טעמא דרבי? דתניא: ״כי דבר ה׳ בזה״⁠ – זה הפורק עול ומגלה פנים בתורה. ״ואת מצותו הפר״⁠ – זה המפר ברית בבשר. ״הכרת תכרת״⁠ – הכרת לפני יום הכפורים, תכרת לאחר יום הכפורים.

The Talmud asks: What is the reasoning of R' Yehuda HaNasi? It is as it is taught in a baraita in interpretation of the verse: “For he scorned the word of YHWH and nullified His commandment; that person will be cut off [hikkaret tikkaret], his sin is upon him” (Numbers 15:31): “For he scorned the word of YHWH”; this is referring to one who divests himself of the yoke of Heaven and one who reveals facets of the Torah that differ from its true meaning. “And nullified His commandment”; this is referring to one who nullified the covenant of circumcision of the flesh. The use of the double verb form hikkaret tikkaret teaches that he will be cut off, i.e., he is liable to receive karet, before Yom Kippur, and he will still be cut off after Yom Kippur, as Yom Kippur does not atone for him.