What is “Sexual Immorality” in Matthew 19:9?

From Genesis to Revelation, the Bible repeatedly stresses the fact that God designed the institution of marriage (Genesis 2:22-25). He has, from the beginning of human history, given very specific ideas about what composes a divinely approved marriage (Matthew 19:1-4), consisting of one man and one woman. We learn from the Scriptures, however, that not every man or woman is qualified to enter into certain marital relationships. In the New Testament, we read of three, and only three, categories of people whom God approves to enter into marriage. The first category is those who have never been married (Hebrews 13:4). The second category of people who are eligible to marry is those who have been married but whose spouses have died (Romans 7:1-3). The third category of God-approved marriage candidates is those whose spouses have committed “sexual immorality” (Matthew 19:9). It is to this last category and to the term “sexual immorality” that we will direct our attention.

In Matthew 19:1-10, Jesus was tested by the Pharisees with the following question: “Is it lawful for a man to divorce his wife for any reason?” Jesus responded by directing their attention to God’s original creation of Adam and Eve. They then queried why Moses allowed certificates of divorce if marriage was supposed to be such a permanent institution. Jesus responded:

Moses, because of the hardness of your hearts, permitted you to divorce your wives, but from the beginning it was not so. And I say to you, whoever divorces his wife, except for sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery (Matthew 19:8-9).

Notice, from this verse, that any person who gets a divorce for any reason other than sexual immorality, and marries another, commits adultery. But a person who divorces his/her spouse for sexual immorality and marries another person does not commit adultery. Thus, Jesus gives the criterion for those who are in the third category of God-approved marriage candidates. Also notice those who are not eligible to enter into a marriage: anyone who has gotten a divorce for any reason other than sexual immorality. [NOTE: The parallel passage found in Matthew 5:32 quotes Jesus as saying: “But I say to you that whoever divorces his wife for any reason except sexual immorality causes her to commit adultery; and whoever marries a woman who is divorced commits adultery.”]

With Jesus’ statement in mind, it becomes imperative to learn what the term “sexual immorality” means, since this is the only infraction on behalf of a spouse that would allow for the remarriage of the innocent party (the spouse who does not commit sexual immorality) after a divorce. As you can imagine, in our culture of rampant divorce and remarriage, and secularized Christianity, this word has been given all sorts of meanings in an attempt to allow virtually every divorced person to be considered a God-approved candidate for remarriage. Many of these definitions are nothing more than attempts to alter the Word of God. So then, what does “sexual immorality” mean?

In order to understand what Jesus was saying, we must go back to the original language and identify what the word meant in the first century. The word translated “sexual immorality” in this verse is the Greek word porneia. The respected Greek lexicon of Arndt, Gingrich, and Danker states that the word refers to “prostitution, unchastity, fornication, of every kind of unlawful sexual intercourse.” In their primary definition, they mention that it refers to “the sexual unfaithfulness of a married woman” (1979, p. 693). The NIV Theological Dictionary of New Testament Words has an extensive section on porneia and related words: “This word group describes various extramarital sexual modes of behavior insofar as they deviate from accepted social and religious norms (e.g., homosexuality, promiscuity, pedophilia, and esp. prostitution)” (Verbrugge, 2000, 6:1077). This dictionary further notes: “Rab. Jud. (Rabbinical Judaism—KB) frowned on any kind of prostitution of extramarital sexual intercourse. Incest and all kinds of unnatural sexual intercourse were viewed as porneia (6:1078). In the discussion of the word’s use in the New Testament, the volume states:

It is not clear whether porneia in the so-called ‘exceptive clause’ (Matt 5:32; 19:9) is to be understood simply as extramarital sexual intercourse in the sense of moicheia or as including prostitution. Most interpreters tend to favor the former interpretation…. The porne word group denotes any kind of illegitimate sexual intercourse in Paul’s letters (6:1078, emp. added).

TheTheological Dictionary of New Testament Words says concerning this word group that the “NT is characterized by an unconditional repudiation of all extra-marital and unnatural intercourse” (Hauck and Schultz, 1968, 6:590). In discussing the word as it is used in Matthew 5:32 and Matthew 19:9, this source states: “In both verses porneia refers to extra-marital intercourse on the part of the wife, which in practice is adultery” (6:592). From a survey of the lexical information regarding the word, the almost universally understood meaning of the word porneia is illicit physical sexual intercourse with someone who is not the person’s God-approved spouse (this would include homosexuality and beastiality). In modern terminology, then, the text is simply saying that the only time a person can divorce his or her spouse and marry another is if that spouse has been involved in a sexual affair with someone else. With knowledge of this word’s actual meaning, let us examine how some have attempted to redefine the term. [NOTE: Mark 10:11-12 is evidence of the fact that the Scripture applies both to a man who divorces his wife and to a woman who divorces her husband. The divine regulations apply equally to both genders. See Lenski, 1998, p. 734.]

Any Type of Lewd or Licentious Behavior

In our modern culture the term “pornography” has a host of meanings. It includes pictures of scantily clad men and women, videos of people engaged in illicit sexual situations, posters of women or men “baring it all,” etc. The word “pornography”derives from the word porneia. One can see the obvious connection. Due to the fact that “pornography”seems so similar to porneia, many have come to believe that any actions or behavior that modern people would term pornography would also fall under the definition of porneia. Thus, they suggest that if a person were to look at a pornographic movie, he would be guilty of porneia. If a wife were to send a man who is not her husband text messages with photos of herself in her underwear, or with messages that talk about sexual situations, she would be guilty of porneia. If a spouse were to call a phone-sex line and listen to a sexual situation described to him, he would be guilty of porneia. And the list could go on and on.

The problem with this line of reasoning is that it projects a definition of the word porneia onto the first-century Greek term that the word in the first century did not have. Notice that in the definition provided from the lexical resources, there is near universal consensus that the term meant “sexual intercourse.” Due to the way the term “sex” has been overly applied to modern activities such as “phone sex,” or “sexting,” and “sexy,” the modern understanding is that anything that would be “sexually arousing” would be included in the term “sex.” But the term porneia would not have been understood to have such a loose, broad meaning.

It should be noted, of course, that many of the activities that have been described such as “sexting” or phone sex would be sinful and would be included in numerous lists of thoughts and actions that Christians should avoid. The terms for such activities include licentiousness, lusts (1 Peter 4:3), or lewdness (Romans 13:13). These terms have a much broader definition than porneia. Since that is the case, if Jesus had wanted to use one of these terms with a broader definition than “sexual intercourse” He could have, but He chose not to. As Wayne Jackson correctly stated: “Bible translations that render porneia more generically (e.g., ‘sexual immorality’) are misleading. There are various forms of sexual immorality (e.g., exposing one’s body in seductive clothing) that do not fall under the definition of fornication, though clearly they are sinful” (n.d.).

We get a definite understanding of how first-century Jews understood the term in John 8. In that passage Jesus accused the Jews of being the children of the devil, because they were behaving in the same way the devil would behave. They responded to His accusation by saying, “We were not born of fornication, we have one Father—God” (John 8:41). The word translated “fornication” in this verse is porneias. Notice their understanding of the term porneias included the idea that a person could be born of porneias. That would imply that the term must mean more than looking at pornographic pictures or explicit conversations about sex. In this context, it would be narrowly defined as sexual intercourse that has the biological ability to produce offspring. [NOTE: While the Jews had “spiritualized” the term and applied it to their spiritual relationship with God, that does not change the meaning of the word as they understood it. They certainly meant that they were not “illegitimate” spiritual children born as the result of an extra-marital sexual encounter. The fact that the term was figuratively applied to a spiritual relationship does not alter its literal meaning. See the section of this article titled “Sexual Immorality Used to Describe Idolatry.”]

The response to this statement from those who desire to view porneia as having a broader meaning is that “sexual intercourse” is such a difficult concept to define. Obviously, they say, homosexual behavior cannot produce offspring. Bestiality cannot produce offspring. So, according to them, any attempt to put limits on the nature of such “sexual” activity is doomed to failure. Such reasoning has at least two glaring flaws. First, it misses the point that the word porneia had a first-century meaning that was understood in the context as extra-marital sexual intercourse. Second, such reasoning fails to take into account the fact that in order to accept a broader definition for the term porneia, positive evidence must be presented that shows the word was understood in the first century to have the looser meaning. It is not enough to say, “I really feel like the term would include looking at pornography, sexting, or phone sex.” Any person who believes such activities would be included in the definition must present lexical information and first-century usages of the word that show such activities could be a part of the word’s meaning. Without this type of positive proof, we must stick with the definition that can be shown from the Bible and lexical sources to have been in use in the first-century.

Practically speaking, then, suppose a wife were to confide in a preacher that her husband is viewing pornography and masturbating. She asks the preacher if these transgressions would allow her to scripturally divorce her husband and be a candidate to remarry. The preacher then explains that porneia is the only divinely sanctioned cause for divorce and subsequent remarriage. The woman wants to know if porneia would include what she has described. The preacher shows her the lexical information and biblical usage and explains that “sexual intercourse” is the key component of the word. The woman argues that masturbation could be included in the term “sexual intercourse.” The preacher then goes to John 8:41, explains how the word was used there, and asks the woman to do some study and try to find any instance in or around the time of the first century where we know for a fact the word was used for masturbation or viewing pornography. If such a usage is not forthcoming, the only proper course of interpretation is to exclude masturbation and viewing pornography from the definition of porneia.

What About Matthew 5:27-28?

Once it has been clearly established that porneia is the only exception given for a spouse to scripturally divorce and contract a subsequent marriage, some then turn to Matthew 5:27-28 to broaden the meaning of porneia. Those verses record Jesus saying: “You have heard that it was said to those of old, ‘You shall not commit adultery.’ But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart.” The reasoning is, if a man lusts for a woman other than his spouse, Jesus says he has committed adultery with her “in his heart.” Since he commits mental/heart adultery, the argument goes, that must mean his wife could divorce him for “adultery” based on his lustful thoughts, and she could contract another scriptural marriage. This argument is flawed on several levels.

First, notice where Jesus said the “adultery” takes place: “in his heart.” In Matthew 5:27-28, however, Jesus makes a distinction between what He is saying in Matthew 5:32 and Matthew 19:9. In neither of the latter two instances does Jesus allow for the adultery to be in any other realm but physical. The word porneia carries no inherent meaning that would cause the reader to interpret it to mean anything other than physical sexual intercourse. Since “in his heart” or other such phrases are not included in Matthew 5:32 or 19:9, correct interpretation rules would require us to define the word porneia in physical terms, not mental or spiritual ones. As Wayne Jackson correctly stated: “A fundamental principle of Bible interpretation is that words must be interpreted literally unless there is compelling reason for assigning them a figurative meaning. The term ‘adultery’ is not employed in a metaphorical sense in Matthew 19:9” (n.d.).

Second, we must recognize that while certain sins may carry the same spiritual weight, they do not have the same physical consequences. In Matthew 5:21, Jesus explained that the Old Testament prohibited murder. He elaborated on this concept when He insisted that any person who hates his brother enough to say, “You fool,” will “be in danger of hell fire” (Matthew 5:22). The inspired writer John said: “Whoever hates his brother is a murderer, and you know that no murderer has eternal life abiding in him” (1 John 3:15). From these passages it is clear that the sins of hatred and murder carry the same spiritual weight, but they do not carry the same physical consequences. In the Old Testament, murder was a capital offense punishable by death, but hatred was not. Again, physical adultery was a crime punishable in the Old Testament by stoning, but lust was not. In Matthew 19:9, the sin of porneia may carry the same spiritual weight as lust “in the heart,” but the verses never hint at the idea that the terms carry the same physical consequences. The physical consequences of a spouse committing porneia are that the innocent spouse can divorce that person and contract a new scriptural marriage, while the guilty party must remain unmarried for the rest of his or her life. The same physical consequences are not enumerated for “adultery in the heart” in Matthew 5:28.

Sexual Immorality Used to Describe Idolatry

In a similar way, some have contended that because God used the terms “adultery,” or “sexual immorality,” or equivalent ideas to describe the Israelites’ apostasy into idolatry (Hosea 4:11-13), then the terms can have a broader meaning. They argue that if God’s people can commit “adultery” against Him by worshipping idols, then the word “adultery” must have a meaning broad enough to include activities other than actual, physical intercourse.

Again, this type of argument fails for at least two primary reasons. First, it is clear from the context of Matthew 19:1-9 that the physical relationship between a husband and wife is under discussion. Respected linguists Vine (1985) and Thayer (1962, p. 532) concur that  when not used metaphorically (in reference to idolatry) porneia is used of “illicit sexual intercourse.” There is no discussion in this context of idolatry or spiritualized unfaithfulness. The text could not be clearer in regard to the physical marriage relationship.

Second, the spiritualized, figurative sense of the word makes no sense if the Jews did not understand the physical sense as the primary, literal meaning. For instance, in Hosea 4:12, in regard to Israelite idolatry, the prophet said: “Therefore your daughters commit harlotry and your brides commit adultery.” In a physical sense, what do the terms “adultery” and “harlotry” mean?—illicit sexual intercourse. Without the understanding of the physical meanings, the illustration that God used makes no sense—that in a figurative sense, Israel is married to God, and idolatry is a spiritual act of unfaithfulness. Unless adultery really does mean committing sexual sin against one’s spouse, God’s illustration breaks down.

For instance, consider the statement: “The debater blew his opponent’s argument out of the water.” This figurative use of the phrase only makes sense if we understand the physical picture of literal water and some type of blasting explosion. The figurative use of the word is always dependent on the physical meaning of the term. The physical meanings of the terms are necessarily logically prior to the figurative or spiritualized meanings. Thus, spiritual “adultery” can only be understood if we comprehend the physical use of the term “adultery.” And we have sufficiently established that the physical use of porneia means illicit sexual intercourse.

Finally, and worthy of serious consideration, is this fact: even if it could be shown that porneia might have a spiritualized, figurative meaning in Matthew 19:1-9 (which it cannot), that fact would only indicate a possible use of the word. The one contending that a person could contract a God approved divorce and subsequent remarriage would have to prove that this spiritualized usage is being applied, not just that it is a possibility.If that usage cannot be proven beyond the shadow of a doubt, then a person would be risking his or her soul on a mere possibility. What kind of ground would a person be standing on in the Day of Judgment contending with God, “But I thought the word possibly could have meant…,” when we have a very clear meaning of “physical sexual intercourse” that we know the word carries.


Marriage is permanent. The only two situations in the New Testament in which a person can get married more than once with God’s approval are when a spouse dies, or when an innocent spouse divorces a spouse for porneia. The term porneia means unlawful, physical sexual intercourse. In an attempt to broaden the category of those who can scripturally remarry, some have attempted to define the term porneia with concepts such as viewing pornography or “phone sex.” While those activities are sinful, they are not porneia as the word was used in the first century. Others have contended that lust results in “adultery in the heart” and would be grounds for a scriptural divorce and remarriage. But they fail to differentiate between sins that have the same spiritual weight but have different physical consequences. Jesus’ sole exception for divorcing a living spouse and marrying another is if that spouse has committed physical sexual intercourse with another biological being.


Arndt, William, F.W. Gingrich, and Frederick W. Danker (1979), A Greek-English Lexicon of the New Testament and Other Early Christian Literature (Chicago, IL: University of Chicago Press), second revised edition.

Hauck, F. and Siegfried Schultz (1968), porneia, Theological Dictionary of the New Testament, ed. Gerhard Kittel (Grand Rapids, MI: Eerdmans).

Jackson, Wayne (No Date), “Is ‘Lust’ the Equivalent of ‘Fornication’”, Christian Courier,

Lenski, R.C.H. (1998), The Interpretation of St. Matthew’s Gospel (Minneapolis, MN: Augsburg).

Thayer, Joseph (1962), Greek-English Lexicon of the New Testament (Grand Rapids: Zondervan).

Verbrugge, Verlyn (2000), The NIV Theological Dictionary of New Testament Words(Grand Rapids: Zondervan).

Vine, W.E. (1985), Vine’s Expository Dictionary of Biblical Words (Nashville: Thomas Nelson, Electronic PC Study Bible Version).


A copied sheet of paper

REPRODUCTION & DISCLAIMERS: We are happy to grant permission for this article to be reproduced in part or in its entirety, as long as our stipulations are observed.

Reproduction Stipulations→