a sexually immoral man: someone whose sexual conduct falls outside the boundaries God set for marriage
In the New Testament this word names a man by his sexual behavior: one whose sex life falls outside the limits God set. It is a broad label, not the name of a single act. Depending on the setting it can gather up sex outside marriage, adultery, incest, use of prostitutes, same-sex acts, and even marriage outside the covenant people. The writers reach for it in warning lists and in solemn statements about who will and will not share in God's kingdom.
The word traveled a long way to reach that meaning. In older Greek it meant a male prostitute, a man who sold the use of his body, and the ordinary Greek reader would have heard exactly that. Jewish writers in the centuries before the New Testament stretched the whole family of related words to cover every kind of sex their Scriptures forbade, and by the time Paul used it, this wider meaning was the one his readers assumed.
It helps to set it beside the narrower word for an adulterer, a man who violates a marriage. That word points at one specific offense; this word is the larger basket that holds the rest. So when a list names both, as several do, the sexually immoral man is everyone whose sexual life is out of bounds in some other way.
The force of the word is that it describes a settled pattern rather than a single stumble. It marks out a man by the direction his life has taken, which is why it turns up in lists of the kinds of people who, unchanged, place themselves outside God's people.
Why Hebrews 12:16 calls Esau sexually immoral, since the Old Testament never describes him as such.
- majorityThe label draws on Jewish traditions of the time that treated Esau's marriages to foreign, Canaanite women as sexual immorality, so he counts as sexually immoral because he married outside the covenant.; W. Lane, Hebrews 9-13 (WBC 47B, 1991), 455-56; H. Attridge, Hebrews (Hermeneia, 1989), 368-70; C. Koester, Hebrews (Anchor Bible, 2001), 531-33
- minorityThe word is used figuratively: Esau sold off his birthright and so was unfaithful in a spiritual sense rather than a sexual one.; D. Allen, Hebrews (New American Commentary, 2010)
- minorityThe sentence structure keeps the word from describing Esau at all, so that only the charge of being unspiritual, not the charge of sexual immorality, is applied to him.; F. F. Bruce, The Epistle to the Hebrews (NICNT, rev. ed., 1990)
Disputed
How broadly the word reaches in the New Testament, and whether it keeps its older Greek overtone of male prostitution.
- majorityIt is a broad ethical label for any sexually immoral man, having inherited the wide meaning that Jewish writers gave the whole word family; its "male prostitute" origin has dropped away.; BDAG, s.v. πόρνος; Louw-Nida, Greek-English Lexicon of the NT Based on Semantic Domains, §88.271; K. Harper, "Porneia: The Making of a Christian Sexual Norm," JBL 131 (2012): 363-83
- minorityIt never fully loses its narrower core tied to prostitution or the exploitation of sex, so "sexually immoral man" is too vague, especially where a list also names commercial sexual wrongdoing.; D. B. Martin, Sex and the Single Savior (Westminster John Knox, 2006), 125-47; D. Wheeler-Reed, J. W. Knust, and D. B. Martin, "Can a Man Commit πορνεία with His Wife?" JBL 137 (2018): 383-98