Various kinds of irregular sexual relationships are covered by this word but the OT takes a fairly relaxed view of most of them. Rahab the harlot is far from being stigmatized (Josh. 2); she comes in the genealogy of Jesus (Matt. 1: 5). But Lev. 18 represents a harsher attitude. Advice to young men after the Exile was that irregular relationships are inadvisable (Prov. 7: 5–27); but where associated with religious prostitution or heathen rites opposition is total (Lev. 21: 7, 9).
In the NT a metaphorical use is common (e.g. Matt. 12: 39) as well as the literal use (1 Cor. 6: 18). Fornication is condemned as being incompatible with the sovereignty of God, whose intention is to restore all mankind in undivided loyalty to himself. Nevertheless Jesus taught that in the Kingdom outcasts and prostitutes would take precedence over the self‐righteous (Matt. 21: 31 ff.).