Adultery

conjugal infidelity. An adulterer was a man who had illicit
intercourse with a married or a betrothed woman, and such a
woman was an adulteress. Intercourse between a married man and
an unmarried woman was fornication. Adultery was regarded as a
great social wrong, as well as a great sin.

The Mosaic law (Num. 5:11-31) prescribed that the suspected
wife should be tried by the ordeal of the "water of jealousy."
There is, however, no recorded instance of the application of
this law. In subsequent times the Rabbis made various
regulations with the view of discovering the guilty party, and
of bringing about a divorce. It has been inferred from John
8:1-11 that this sin became very common during the age preceding
the destruction of Jerusalem.

Idolatry, covetousness, and apostasy are spoken of as adultery
spiritually (Jer. 3:6, 8, 9; Ezek. 16:32; Hos. 1:2:3; Rev.
2:22). An apostate church is an adulteress (Isa. 1:21; Ezek.
23:4, 7, 37), and the Jews are styled "an adulterous generation"
(Matt. 12:39). (Compare Rev. 12.)