to commit sexual immorality: to actually engage in sex that falls outside the boundaries the law of Moses set for marriage
This is the verb of a family of Greek words built on the picture of prostitution. The noun (πορνεία) names the immorality itself, and this word names someone actually doing it. It is rare, appearing only eight times in the New Testament, and every time it is something a writer is telling readers to stop or to avoid.
In ordinary Greek the verb was narrower and more concrete: to sell the use of one's own body, which is what a prostitute (πόρνη) did for a living. Jewish writers in the centuries before the New Testament stretched the whole family to cover any sex their Scriptures forbade, so by the time Paul used it the verb reached well past the brothel to adultery, incest, and forbidden marriages.
Two settings account for the uses that describe real sexual conduct. Paul tells the Corinthians to run from it, in a port city where paying a slave prostitute was assumed to be harmless. Then three times the verb stands next to eating food offered to idols: Israel's sin at Peor, Balaam's scheme to trap Israel, and the teaching of the woman called Jezebel at Thyatira. In that second group sexual sin and idol worship are not two problems but one, which is also why this verb slides so easily into a picture of unfaithfulness to God.
Nuances
Whether the verb in Revelation 2:14 describes actual sexual conduct at pagan gatherings or is an image for compromising with idolatry.
- contestedReal sexual behavior is in view, since meals at Hellenistic trade guilds and civic festivals commonly involved sexual revelry, and the verb sits beside the literal eating of food offered to idols.; David E. Aune, Revelation 1-5 (WBC 52A; Word, 1997), 203-208
- contestedThe verb is primarily figurative here, naming an illicit intimacy with idols rather than a sexual act, in continuity with the prophetic use of harlotry language.; G. K. Beale, The Book of Revelation (NIGTC; Eerdmans, 1999), 248-262
- contestedThe two readings are not exclusive: the language points at real conduct at pagan meals and works at the same time as an image of unfaithfulness to God.; Craig R. Koester, Revelation (AYBC 38A; Yale University Press, 2014), 285-290
Whether the verb in Revelation 2:20 charges the followers of the woman called Jezebel with actual sexual conduct or with religious compromise described in sexual language.
- contestedReal sexual conduct at trade-guild and civic banquets is in view, alongside the literal eating of food offered to idols.; David E. Aune, Revelation 1-5 (WBC 52A; Word, 1997), 203-208
- contestedThe verb is primarily figurative, naming an illicit intimacy with idols in continuity with the prophetic harlotry image.; G. K. Beale, The Book of Revelation (NIGTC; Eerdmans, 1999), 248-262
- minorityThe charge is polemical sexual language aimed at a rival prophet who urged Christians to accommodate themselves to Greek and Roman civic life, not a report of sexual behavior.; Paul B. Duff, Who Rides the Beast? Prophetic Rivalry and the Rhetoric of Crisis in the Churches of the Apocalypse (Oxford University Press, 2001), 50-95