The seventh commandment of Ex.20.14 and Deu.5.18 is quoted in Mt.5.27, 19.18, Mk.10.19, Lk.18.20, Rom.13.9 and Jas.2.11, the Greek word moicheia (3430) being used to translate the Hebrew word na'aph (5003). Lev.20.10 uses na'aph to describe something wrong a man does concerning his neighbor's wife.
The context through v.21 lists punishments for various sexual sins.
Thus the meaning of na'aph in v.10 may involve "sexual immorality" (Greek: 4202 porneia) with the neighbor's wife, but it could also mean "unfaithfulness" to his own wife (Greek: a 3428-32 "moich" word), or both.
In Jer.3.6-10 the nations of Israel and Judah are personified, with Israel having committed "na'aph," and having been "put away" and "given a bill of divorcement" by God.
Although sexual sin is involved, the primary thrust of v.8 appears to be Israel's unfaithfulness to God.
Unfaithfulness to God or God's law is involved In every passage in which na'aph is used, and often also unfaithfulness to a spouse.
A comprehensive word-study of na'aph would include a word such as "unfaithfulness" as a primary definition.
Looking at the Jewish culture for example we see that the commandment of not eating a "kid boiled in its mothers milk" is taken "by extension" to mean that one should not eat dairy with meat. Therefore, no lasagna or cheeseburgers for Jew.
The point of this being that such extensions are not unheard of, particularly where the meaning is so obvious.
As Etymology of the word reveals:
The word adultery originates not from "adult", as is commonly thought in English-speaking countries, but from the late latin word for "to alter, corrupt": adulterare.
Adulterare in turn is formed by the combination of ad ("towards"), and alter ("other"), together with the infinitive form are (making it a verb). Thus the meaning is literally "to make other". In contrast, the word "adult" (meaning a person of mature years) comes from another Latin root, adolescere (or adulescere), meaning to grow up or mature: a combination of ad ("towards"), alere ("to nourish", "to grow"), and the inchoative infix sc (meaning "to enter into a state of").
The application of the term to the act appears to arise from the idea that "criminal intercourse with a married woman ... tended to adulterate the issue [children] of an innocent husband ... and to expose him to support and provide for another man's [children]". Thus, the "purity" of the children of a marriage is corrupted, and the inheritance is altered. The law often uses the word "adulterate" to describe contamination of food and the like.
(So mr. dogbrain, why would this word be chosen to translate the concept which we read in the scripture????
If adulteration has nothing to do with it then why is this the case?
Why not chose another word which only refers to infidelity in a sexual sense?)
Jesus taught that indulgence in adulterous thoughts could be just as harmful to the soul as sexual adultery, and it is clear that both carry the same weight of guilt:
But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.
Why does it not say that such a one has committed sex with the woman if that is what the central idea is, unless the central idea is something else. So all this points clearly to a bigger idea which the obvious example of sexual purity is used to illustrate.
This is used as it is so intimate an issue which will be easy to relate to.
Sexual infidelity is common and always has been so.
Therefore people can relate to it easily.
It causes much harm, therefore it is a good example of the principle of breaking one's word, violating covenants, of bringing in impurity and corruption, etc.
Looking at the Bnai Noach 7 commandments we see that commandment # 7 is : "Requirement to have just laws: Set up a governing body of law (eg Courts)".
But the thing is, only the basics are covered in scripture.
Not an extensive law book which covers in detail all matters of justice, exactly, yet it does so by setting the pace for what justice really is.
From this we get a picture of what justice is, as well as righteousness, from which, by extension, we can formulate laws that reflect such ideals.
If you buy a bottle of water, but it has been adulterated by a careless or devious merchant, do you feel that you have been justly treated?
Or have they been unfaithful in principle to you?
I know mine was really keen on a good rabbit chase.