FORNICATION
(from the Greek “porneia”, primarily fornication, any sexual practice outside of marriage, and also, figuratively, idolatry, apostasy, etc.).
In its various forms it appears 447 times in the New Testament. Four times at least its meaning is obvious; thus, in 1 Cor. 7:2 and 1 Thes. 4:3, Paul admonishes singles to guard against the temptation to fornicate.
In both passages Paul defends marriage as a prevention of immorality. In four other cases “fornication” is used in a list of sins that also contains “adultery” (Mt. 15:19; Mark 7:21; 1 Cor. 6:9; Gal. 5:19). In at least two other cases it is used as a synonym for adultery (Mt. 5:32 and 19:9).
The body is the temple of the Holy Spirit; Paul exhorts believers to flee fornication (1 Cor. 6:18; cf. 1 Cor. 6:13). Here the term refers to all immorality of the body, and Christ said in this regard that all sexual immorality has its origin in the heart of man (Mt. 5:28; Mark 7:21); Therefore, we must take care of the heart (Prov. 4:23; Jer. 17:9).
In a figurative sense, fornication refers to all forms of apostasy and the immoral relationship of a believer with other gods.
In other New Testament passages “fornication” is used in a general sense referring to all forms of lasciviousness (John 8:41; Acts 15:20; Rom. 1:20; Eph. 5:3). There are uses that refer to prostitution and sexual commerce (Rev. 2:14, 20, 21).