The Mishnah (Keritot 1:1) lists 36 prohibitions for which the Bible prescribes the punishment of karet (if one sins willfully).
In Yeriot Shlomo, Rabbi Shlomo Pappenheim of Breslau (1740-1814) counts “karet” among 15 Hebrew words for cutting. “Karet,” he writes, is a general word for cutting and is used to designate, among other things, a get. The Torah calls it a “sefer kritot” – literally, a “book of cutting” (Deuteronomy 24:1) since a marriage joins two people while a divorce tears them apart.
“Karet” is also used to denote the ratification of a treaty since parties in ancient times would cut animals in half and walk between them to seal a deal. Interestingly, some linguists link this custom to the English idiom “to cut a deal.”
In Cheshek Shlomo, Rabbi Pappenheim writes that the root of “karet” is kaf-reish, which denotes a type of “digging.” Just as digging breaks up and separates different grains of dirt, so, too, cutting separates different pieces from each other.
Rabbi Yaakov Tzvi Mecklenburg (1785-1865) writes that the punishment of karet entails being “cut off” from the World to Come in which all souls reunite with G-d. One is isolated from that eternal rapture and does not join everyone else.
Rabbi Chaim of Volozhin (1749-1821) asserts that karet means a soul is cut off from its Upper Source (Nefesh HaChaim 1:18). He maintains that a soul enjoys a lifeline – a sort of Divine umbilical cord – that connects it to its Creator. When one commits a sin and is punished with karet, 9/10 of that cord is cut. (The cord itself is never completely severed.)
Nachmanides and Rabbeinu Bachaya (to Leviticus 18:29) write that there are three types of karet. One affects the body, another affects the soul, and still another affects both. The first one affects a person who violated a karet-level prohibition but has more merits than sins. He dies early, but his soul enters the World of the Souls and will return during the Resurrection of the Dead.
The second one affects a person who violated a karet-level prohibition and has accrued more sins than merits on his record. He may live a long and happy life, but his soul will be barred from the World of the Souls.
The third type of karet affects a person who violates the Torah’s ban on avodah zarah. The Torah uses a double expression to express the karet given to an idol worshipper (Numbers 15:31), which indicates that he gets two types of karet: he will die young and his soul will be punished posthumously.
How young is young? The Talmud Yerushalmi (Bikkurim 2:1) says 50 or under. The Talmud arrives at this number by citing Numbers 4:18: “Do not cut off the tribe of the families of the Kohatites from amongst the Levites.” The Torah tells us that Levites only served until the age of 50 (Numbers 8:25). Putting two and two together, the Talmud derives that the age of being “cut off” cannot be greater than 50.
The Babylonian Talmud (Moed Katan 28a) disagrees and says a person who deserves karet can live up to the age of 60. The Talmud relates that when Rav Yosef turned 60, he made a party to celebrate the fact that he could no longer receive karet. The Talmud ultimately concludes, though, that a person above 60 can be punished with karet in the form of sudden death.
The Ibn Ezra (to Genesis 17:14) explains that karet means a person will die before the age of 52 or that his descendants will die in such a manner that his own memory will be completely erased. In the latter case, the sinner’s legacy is “cut off” from continuing.
The Torah refers to a punishment that seems identical, or similar to, karet with the word “ariri.” It appears only four times in the Bible. When Avraham questions G-d’s promise that he will inherit the Holy Land, he says, “But I am going childless (ariri)…” (Genesis 15:2), and when G-d curses Jeconiah with childlessness, his fate is said to be “ariri“ (Jeremiah 22:30). (According to rabbinic tradition, Jeconiah later repented, and his punishment was overturned. In fact, some sources say the Messiah will be his descendant.) “Aririm“ also appears twice as a punishment for those violating the Torah’s bans on forbidden marriages (Leviticus 20:20-21).
Rashi (to Shabbos 25b) maintains that karet can also affect one’s children, but a Tosafist known as Riva argues that only ariri does. In other words, while Rashi argues that every karet can include ariri, Riva maintains that karet and ariri are separate punishments.
We should note that even Rashi agrees that if one’s children are adults, and do not follow in their father’s sinful path, their father’s karet cannot affect them (see Tosafot Yeshanim to Yevamot 2a).