Did Cain Marry His Sister?

　　After the world was formed, God finished His work of creation by raising one man from the dust and one woman from the man’s ribs. (Genesis 2:21-22) The Lord made only two people, so the only people available for Adam and Eve’s sons to marry were their own sisters. Consequently, although this is not stated, the only logical conclusion is that Cain married his sister and they had children together.

　　

If Cain Married His Sister, Would it be Considered Incest?

By modern legal definition, Cain would have had to commit incest with one of his sisters in order to create offspring because he had no other choice. “If the entire human race came from an original pair then this was unavoidable,” according to Don Stewart.

　　By biblical standards,however, Cain was not breaking any laws because these did not exist at the time. God formed woman from the rib of man so that “a man leaves his father and mother and is united to his wife, and they become one flesh” (Genesis 2:24). In other words, children and parents are not to have sexual relations with or marry each other; yet, no actual laws about incest were given in the unspoiled world of Eden before the Fall, or even before the Exodus.

　　

What Is God’s Law against Incest?

After the Exodus, God commanded “none of you shall approach any one of his close relatives to uncover nakedness” (Leviticus 18:6). But Cain was not subject to that law. “The regulations of the Law of Moses were binding only upon those to whom it was given at the time,” according to the Christian Courier.

　　Even so, “God has never approved of indiscriminate sexual activity outside of the marriage relationship in any age of human history” including incest because “it strikes at the soundness of the family. And since the family is central to God’s purposes and work on earth, his judgment on this practice is fierce” as stated in the Christian Courier.  

　　God also forbade incest to prevent genetic deformities which are less common in the general population, where intermarriage is not typical. Let’s explore these two points.

　　

Why Does God Forbid Incest? Reason 1: It Destroys God’s Design for Family

Don Stewart explains “the commandment against [incest] strengthened the structure of the family unit.” One way to understand what he means is to examine what happens to victims and witnesses of incest.

　　In the case of consensual incest, there is a possibility that one or both parties are acting out the negative effects of previous sexual abuse suffered personally or witnessed as a child. These individuals are “at an increased risk for revictimization,” often unconsciously, according to the website, and for them, the “line between involuntary and voluntary participation in sexual behavior is blurred.”

　　Whether sexual sin is involved or not, creating a strong and safe family unit becomes much harder in the wake of incest.

　　

Lot’s Daughters: An Example of the Consequences of Incest

An example of the negative impact of incest can be found as early as Genesis 19 with Lot’s daughters.  They grew up in Sodom and Gomorrah, cities associated with “sexual immorality and ‘unnatural lust,’” according to Britannica. Sexual depravity was so openly displayed that it is reasonable to imagine Lot’s daughters witnessed incest.

　　Genesis 19:13 says God sent angels to destroy the cities because “the outcry to the LORD against its people [was] so great.” After Lot’s family fled God’s destruction, his wife was turned into a pillar of salt as she looked back on the burning cities, and Lot found a cave for his daughters and him to rest in. The girls got their father drunk and had sex with him (Genesis 19:33-35). Although there was no written commandment against incest at this time, Jews knew that sexual union with one’s parent was not part of God’s plan for procreation (Genesis 2:24).

　　The psychological impact on witnesses of sexual sin could help us to understand why Lot’s daughters behaved as they did. Furthermore, they were offered as potential victims of abuse by their father in place of the angels who had visited his home (Genesis 19:8). As currency for exchange in this transaction, could the girls have questioned their value, their identity, and the unity between husband and wife which sex was intended to foster? These girls emerged from a culture of depravity which influenced their behavior in the cave.

　　The girls were witnesses, then potential victims, and finally perpetrators of incest which led to the births of two sons whose futures embodied the destruction of family caused by sexual crime. The sons these sisters bore would start two tribes related to but frequently in conflict with Israel: the Moabites and Ammonites.

　　

What Is God’s Intention for Family?

The original intention of family was to “reflect God's character” but more than that: “it provides a safe place where children can experience God's love (through their parents) and learn how to love other people,” Focus on the Family stated. No family is perfect, but incest destroys and distorts God’s purpose for family. The biblical example above demonstrates the potential for long-term consequences.

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　　Six Prayers for Estranged Family Members

　　

Why Does God Forbid Incest? Reason 2: It Mutates Human Genetics

The more insular a community is, the more prevalent certain diseases will be. Scientists report that “many unique genetic disorders [] result” when communities begin or persist with “small founding populations and cultural isolation,” according to the National Center for Biotechnology Information.  

　　While genetic mutation is not specifically mentioned in Mosaic law, only references to being “unclean” or “defiled” (Leviticus 18:24), Don Stewart asserts that God did not permit intermarriage among his chosen people to lessen the likelihood of genetic issues. “The future health of the nation Israel was insured by this commandment,” Stewartwrote.

　　From the evidence above, one might conclude that God’s plan was flawed from the start. If Cain and his sister had children together, they would have passed on genetic mutations leading to birth defects and a host of diseases. Such a conclusion, however, overlooks the fact that “when God created the world, […] it was very good” and without sin, according to Matt Slick. “There was no suffering. And, there was no pain. It was not until Adam and Eve freely chose to rebel against God, that pain and suffering entered into the world,” he said. Part of that pain and suffering includes disease and deformity.

　　Inter-family procreation is likely to cause genetic deformities today. In the beginning, however, “there would not be the usual genetic defects arising from intermarriage” because “Adam and Eve were created perfect with a perfect gene pool,” Slicksaid. Only later would families see the genetic results of intermarriage inter-family procreation.

　　

God’s Redemption for Broken People

God has made a convincing case against incest and demonstrated that incest is both a cause of and a result of disobedience and pain. God Almighty always has a plan, however.

　　He redeemed the sin committed by Lot’s daughters. Ruth, as a Moabite, traced her genealogy back to Lot and his daughters in the cave in Genesis 19. Jesus’ traced his lineage back to Ruth through the line of His adopted father, Joseph.

　　“God weaves his grace […] through the genealogies” and He “loves to produce something beautiful out of sordid family backgrounds,” Jon Bloomsaid.

　　Although God’s Word offers wisdom and direction in the matter of marriage and sexual behavior in order to protect His children, many people are living with genetic illness, the sin of having committed incest, or the shame of victimization. The bodies of believers will be made perfect in heaven forevermore, but even now, Jesus offers freedom. He can redeem confessed sin, bring peace and hope to a life thrown into chaos by illness, and help victims of sexual crime forgive those responsible and experience emotional freedom.

　　Other Sources:

　　Biblical Archaeology Society, "Who Were the Ammonites, Moabites and Edomites in the Bible?" Megan Sauter, 2019.

　　Blue Letter Bible, "Where Did Cain Get His Wife?" Don Stewart.

　　Candice Lucey lives with her husband and daughters in (mostly) tranquil Salmon Arm, BC, Canada. Here, she enjoys digging into God’s word when not working or taking part in ministry activities. Her prose and poetry has previously appeared in such publications as Purpose and Creation Illustrated, and her short plays were performed at Christmas by Sunday School students for several years. Catch up with Candice’s scriptural studies at her blog Wordwell.ca.