The word fornication is a common English translation (KJV) of the Greek word porneia, from which we derive the word pornography. Translators differ how to best translate this Greek word. The most common English translations are sexual immorality (ESV, NIV, NKJV) and unchastity (NASB, NRSV, RSV). The word porneia occurs in some form twenty-six times in the New Testament (Matt. 5:32; 15:19; 19:19; Mark 7:21; John 8:41; Acts 15:20, 29; 21:25; Rom. 1:29; 1 Cor. 5:1 (twice); 6:13, 18; 7:2; 2 Cor. 12:21; Gal. 5:19; Eph. 5:3; Col. 3:5; 1 Thess. 4:3; Rev. 2:21; 9:21; 14:8; 17:2, 4; 18:3; 19:2). Porneuō, a related verb, occurs eight times in the New Testament. So, the New Testament raises the subject of fornication more than thirty times. The Old Testament Hebrew counterpart is zanah—its root appears more than fifty times in the Old Testament.

In recent decades, there has been significant debate regarding the range of use of porneia. Many attempts have been made to narrow the range of meaning for the word in order to broaden what is allowable with respect to sexual activity. In other words, if the meaning of porneia is restricted to a married person having sexual intercourse with someone who is not his or her spouse, then myriad sexual activities are now fair game both inside and outside of marriage. On the other end, unhappy spouses have attempted to broaden the range of meaning in order to find more justifications for divorce. Since Jesus forbade divorce except in cases of porneia (Matt. 5:32; 19:9), a wife needs only to prove that her husband has gazed at another woman and she’ll have Jesus’ blessing to divorce him. Such attempts to narrow or broaden the meaning of porneia fit our deceptive hearts, letting our evil desires drive our exegesis. But if we care about faithfully interpreting Scripture and if we care about living according to the Lord’s precepts, we need to consider the intended scope that the biblical writers have in mind when they command us to flee from porneia (1 Cor. 6:18; 1 Thess. 4:3).

Part of the difficulty can be accounted for by the fact that the KJV’s translation fornication has all but fallen out of modern English parlance. Sexual immorality and unchastity are also fitting translations, but they still don’t in themselves capture the meaning of porneia. The mere English words do not in themselves tell us all that is included under the umbrella of sexual immorality and unchastity. Not surprisingly, no English word can or will be able to stretch wide enough to cover all that the biblical authors presupposed when they used the term porneia. Sexual immorality perhaps comes closest, but we still must delineate which sexual activities are immoral and which are not.

There’s a close relationship between the New Testament’s frequent call to abstain from porneia and the seventh commandment. What does the seventh commandment forbid? The seventh commandment forbids adultery (Ex. 20:14; Deut. 5:18).

There’s a time for sexual activity, but it’s only after vows are taken, at which point God’s good gift of sex can be enjoyed in its proper context.

The narrow scope of the seventh commandment forbids profaning a marriage covenant by means of sexual encounters between a married person and someone who is not his or her spouse. In its broader scope, however, the seventh commandment restricts any and all sexual activity to the context of the marriage covenant. Paul says in 1 Corinthians 7:1–2 that each man should have his own wife and each woman her own husband because of the temptation to porneia. The clear inference is that porneia is a temptation for unmarried people, too. Accordingly, single people can violate the seventh commandment. If porneia isn’t a temptation only for married people, what activities fall under its umbrella? The Westminster Larger Catechism offers an extensive list of sins forbidden in the seventh commandment:

The sins forbidden in the seventh commandment, besides the neglect of the duties required, are, adultery, fornication, rape, incest, sodomy, and all unnatural lusts; all unclean imaginations, thoughts, purposes, and affections; all corrupt or filthy communications, or listening thereunto; wanton looks, impudent or light behavior, immodest apparel; prohibiting of lawful, and dispensing with unlawful marriages; allowing, tolerating, keeping of stews, and resorting to them; entangling vows of single life, undue delay of marriage; having more wives or husbands than one at the same time; unjust divorce, or desertion; idleness, gluttony, drunkenness, unchaste company; lascivious songs, books, pictures, dancings, stage plays; and all other provocations to, or acts of uncleanness, either in ourselves or others.

Perhaps the Westminster divines perceived the human heart’s tendency to toe the line. “How far is too far?” is a question fielded not only by youth ministers. In recent years, Joshua Harris’ disavowal of his books I Kissed Dating Goodbye and Boy Meets Girl and his public declaration of apostasy that followed in July 2019 have reignited among evangelical Christians the discussion regarding premarital sexual activity. Many have thrown away a concern for sexual purity altogether as a consequence of their repudiation of and disillusionment with the “purity culture” represented by monuments from the 1990s and early 2000s such as Harris’ books. This is demonstrated, for instance, in an August 2019 study showing that about two-thirds of never-married “evangelical young people” state that they have engaged in sexual intercourse.1 To be sure, it is not entirely shocking that professing Christians have succumbed to temptation. Reformed Christians ought to be well acquainted with the struggle in mortifying sinful desires. At times, even Christians fall into grievous sins (see Rom. 7). Thankfully, God is faithful and just to forgive all those who confess their sins—both preconversion and postconversion sins. However, what’s most concerning about these statistics is the relatively lax attitude that professing Christians have toward sexual promiscuity. The same study found that of those young evangelicals who have abstained from premarital sexual intercourse (roughly 33 percent of all young evangelicals), only 42 percent cited religious convictions as the main reason for abstinence. The rest were either waiting for the right time and partner or simply hadn’t yet had the opportunity to engage in premarital sexual intercourse. Such findings are reinforced in the 2018 Ligonier State of Theology survey, which showed that almost 50 percent of professing Christians disagree that or are unsure whether sex outside of marriage is a sin.2 Indeed, many of these findings are shocking, but perhaps even more troublesome is that we can only speculate how high the percentages would be if these studies measured rates of cohabitation, pornography use, or premarital fondling. Yet, just as the seventh commandment isn’t limited in scope to married people (i.e., unmarried people are still required to keep the seventh commandment), the seventh commandment does not forbid only sexual intercourse outside of marriage. Broadly, it also forbids any activity that is intended to arouse and fulfill sexual desires that would naturally lead to sexual intercourse. That means that any activity that arouses lust for sexual pleasure outside of the marriage context ought to be avoided. Such activity, broadly speaking, is a violation of the seventh commandment; it is sexual immorality—porneia.

Consider the Apostle Paul’s admonition that it is “better to marry than to burn with passion” (1 Cor. 7:9). He could have said “it is better to marry than to engage in premarital intercourse.” That statement would certainly be true. Instead, he maintains that marriage is better than burning. The Greek verb here translated as “to burn with passion” means to become aroused or overly excited, often with respect to sexual arousal. Paul expresses that it’s better to marry than to have such arousal, since such arousal is intended to lead to marital intimacy. This is one of the reasons that the Westminster divines declare that an undue delaying of marriage is a violation of the seventh commandment (WLC 139). Solomon similarly issued the adjuration to not “stir up or awaken love until it pleases” (Song 8:4). There’s a time for sexual activity, but it’s only after vows are taken, at which point God’s good gift of sex can be enjoyed in its proper context.

Sexual activity between unmarried people—even of the kind which isn’t intercourse—is the fruit of lust and premature sexual arousal. Such activity is sexual immorality (i.e., porneia) that can (and often does) lead to even more heinous sexual immorality (see 1 Cor. 6:18). (Thus, we must admit degrees of heinousness with respect to fornication; see WLC 150.)

Some may contest that defining fornication or sexual immorality this broadly is legalistic. But that misunderstands what legalism means. We’re attempting to understand God’s law, not add to God’s law. We’re certainly not positing that sexual purity contributes to our being justified before God. Rather, we’re letting the Bible dictate our sexual ethic while resting continually in Christ when we overstep, fall short of, violate, and misapply God’s law. By His Spirit, we strive to walk faithfully in sexual morality and chastity, fleeing from fornication of any kind.


  1. National Survey of Family Growth, cited in David J. Ayers, “Sex and the Single Evangelical,” Institute for Family Studies, August 14, 2019, accessed August 29, 2019, ↩︎
  2. 2018 Ligonier State of Theology Survey, Statement 26. ↩︎

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