The Old Testament
The Hebrew word, "karet", is typically translated into "cut off". A common use is "cut off from the people", which often is the consequence of offences against the law of Moses. This article describes some of these. But there seems to be some uncertainty about what exactly "karet" means. What did/does it really mean in practice to be "cut off from the people"? Perhaps the Book of Mormon can give some clues.The Book of Mormon
The expression, "cut off" is used a lot in the Book of Mormon, but usually not in the context of being "cut off from the people". A common use is one contained in the proverb discussed recently: Cut off from the Lord's presence. Alma 42 uses this expression a lot and can help us understand it better. Verses 6-9:So "cut off", is a way to describe death, either physical or spiritual. "cut off from the presence of the Lord", which is the most common use in the Book of Mormon, is spiritual death. So what is the difference between "cut off from His presence" in the Book of Mormon and "cut off from the people" in the Old Testament? Perhaps not much. 3 Nephi 21 gives us a clue. It quotes and paraphrases from the Old Testament and uses the Old Testament phrase, "cut off from the people" twice6 But behold, it was appointed unto man to —therefore, as they were cut off from the tree of life they should be cut off from the face of the earth—and man became forever, yea, they became man.7 And now, ye see by this that our first parents were both temporally and spiritually from the of the Lord; and thus we see they became subjects to follow after their own .8 Now behold, it was not expedient that man should be reclaimed from this death, for that would destroy the great of happiness.9 Therefore, as the soul could never die, and the had brought upon all mankind a spiritual as well as a temporal, that is, they were cut off from the presence of the Lord, it was expedient that mankind should be reclaimed from this spiritual death.
In verse 11
they shall be from among my people who are of the covenant.and in verse 20
whosoever will not repent and come unto my Beloved Son, them will I from among my people, O house of Israel