If somebody desecrates holy things by taking either korbanot (offerings) that are brought onto the Mizbeach (altar) or objects donated to the Beit HaMikdash and using them for non-holy, non-sacred purposes, he desecrates them in that way. Another case is somebody who desecrates or disgraces the days in between the Yamim Tovim (the holidays) on Pesach and Sukkot, either by working on them or by doing certain things that would not befit a holiday, thereby disgracing the holiday. Another case is somebody who publicly embarrasses another individual and causes his face to turn white. When a person gets embarrassed, his face turns red as the blood rushes to his face. But when he realizes that there is no source or reason for the blood coming to his face other than the embarrassment causing his pain, the blood drains from his face and he turns white. It is such a severe sin that it is comparable to murder. We know that somebody should rather throw themselves into a fiery furnace than commit the sin of murder or embarrass another individual. That is the Gemara's suggestion: You might as well throw yourself into a fiery furnace rather than embarrass somebody else.
Another case is somebody who rejects the idea of a Brit Milah (circumcision) of Abraham Avinu. The person either does not get a Brit Milah when it is his time—his father did not give him one, and when it becomes his time to do it, he does not do it—or he had a Brit Milah but pulls the skin in a way that hides the fact that he has a Milah (circumcision). He rejects this fundamental mitzvah (commandment) of the Jewish people. Another case is somebody who gives explanations of the Torah that go against the normal way that we treat the Pesukim (verses). We have a Torah Shebe'al Peh, we have a tradition on how Pesukim are read. If somebody rejects the meaning of a Pasuk (verse) that we have, which goes back to Sinai, or gives a Halakha (Jewish law) that would not fit with it, the Torah has a certain authenticity that it has to stand for if a person goes against that tradition. Even if this type of person has the Zechut (merit) of Torah study and has a lot of good deeds that he has done as well, he does not have a share in the world to come.
All of these actions that we discussed in the Mishnah are so severe, so egregious, that if a person violates them, he loses his share in the world to come. We learn this from the Pasuk: “He disgraced the word of God.” That part of the Pasuk refers to somebody who disgraces the objects of Hashem, the holy things, or the days of Hashem, the holidays, which are sanctified by Hashem, or somebody who embarrasses another person, who was created by Hashem. So you are disgracing the word of Hashem. A person was created by the statement of God. Likewise, somebody who takes the word of Hashem, which is the Torah, and twists it breaks the word of Hashem. All these types of people lose their share in the world to come.
There is also somebody who violates the part of the Pasuk that continues and says, “He has taken the commandments of Hashem and broken them.” That is somebody who rejects the mitzvah of Brit Milah. The Pasuk says that this type of person is violating it: he should be cut off because the sin is on him. “Cut off” is stated twice. We mentioned that it means once for this world and once for the world to come.
These are foundational ideas. Even though he may have Torah and may have mitzvot (commandments), he has violated the overall picture of what Judaism stands for. He has violated Hashem himself. Therefore, this person loses his share in Olam Haba (world to come).