Christian Sexual Ethics Between the Ages

Is the Christian sexual ethic universal? Is New Testament sexual morality designed only for Christians, or for all people? I suspect most readers will incline to say the Christian sexual ethic is universal. That answer would be correct—mostly.

Is the New Testament’s sexual ethic the same as the Old Testament’s? Many readers will incline to answer that question in the affirmative too. That also would be correct—for the most part.

New Testament teaching on sexuality does correspond to our human nature and thus to God’s original intentions for righteousness in this world. It also echoes Old Testament instruction on sexuality, especially as found in the Mosaic law.

Yet crucial aspects of the New Testament’s teaching are inexplicable apart from the fact that Christ has come, established his new-covenant church, and granted believers an inheritance in his everlasting kingdom. Christians remain human beings but are also now human beings united to Christ and citizens of heaven. Both truths are crucial for understanding and practicing New Testament sexuality.

Created Order

The Christian tradition has long affirmed that sexual morality is grounded in the created order and thus expressed in natural law. At least five aspects of creation-order sexuality can be reasoned from Genesis 1–2.

First, God made humans male and female in his image (1:27).

Second, procreation was an important purpose of their creation as male and female. God called them to “be fruitful and multiply and fill the earth” (v. 28). The Noahic covenant reiterated this command for our fallen world (9:1, 7).

Third, God ordained marriage as a one-flesh union between a man and a woman (2:24). This implies marriage is both an intimate relationship (because it’s sexual) and an enduring relationship (because it entails leaving one’s old family and holding fast to one’s spouse as a new family).

Fourth, extramarital sexual relations contravene this creation-order morality. Extramarital relations are transient and nonexclusive, rather than enduring one-flesh unions.

Fifth, pursuing marital relationships that aren’t between one man and one woman also contravenes the natural order. Homosexual relationships, for example, don’t join a man and a woman, and polygamous and polyandrous relationships don’t make a man and a woman one flesh, since other parties join the intimacy.

As grounded in the natural order, this sexual morality corresponds to human nature. The implications are profound. To live in accord with creation-order sexuality fits the way God made us. God’s designs for sex are good for us, not arbitrary constraints keeping us from having fun.

We do well to communicate this truth. Following natural-law sexuality doesn’t guarantee a fully satisfying sexual life, of course, any more than eating well and exercising guarantees good health. But as a good diet and exercise promote good health, given the way God made us, so also enjoying sex only within faithful marriages promotes stable family life and personal satisfaction in ways alternative relationships simply can’t.

God’s designs for sex are good for us, not arbitrary constraints keeping us from having fun. We do well to communicate this truth.

As the father instructs his son in the prologue of Proverbs, the adulterous woman is initially attractive (5:3) but in the end is bitter and sharp (v. 4), leading the young man to ruin (vv. 11, 14). The adulteress is seductive and smooth (7:14–21), but the one who falls for her is like an ox going to the slaughter or a bird in a snare (vv. 22–23). “Can a man carry fire next to his chest and his clothes not be burned? Or can one walk on hot coals and his feet not be scorched? So is he who goes in to his neighbor’s wife; none who touches her will go unpunished” (6:27–29).

Old Testament Sexual Ethics

Although the Mosaic law permitted certain violations of natural-order sexuality (see Matt. 19:8), such as polygamy and easy divorce, its sexual ethics (and those of the rest of the Old Testament) generally reflect natural law.

The Mosaic law prohibited adultery (Ex. 20:14; Deut. 5:18) and many other extramarital relationships, including incest (Lev. 18:6–18; Deut. 22:30; 27:20, 22–23), male homosexual conduct (Lev. 18:22), prostitution (19:29; Deut. 23:17–18), and bestiality (Ex. 22:19; Lev. 18:23; Deut. 27:21). It maintained gender distinctions as well (see Deut. 22:5).

The fruitful-and-multiply theme is also important in the Old Testament after its initial appearances in Genesis 1 and 9. God’s covenant with Abraham, Isaac, and Jacob repeated the theme multiple times, but with an interesting development. With only one exception (35:11), God promised they’d be fruitful and multiply, rather than merely commanding them to multiply (17:6; 28:3; 48:4). And God said they’d fill not the earth but the promised land of Canaan.

These developments reflected God’s promise to bring salvation through the seed of the woman (3:15) and of Abraham (15:5). When God was about to bring Israel into Canaan, he again promised to make them fruitful and to multiply them (Lev. 26:9).

Getting married and having children was thus the norm for Israel. The Old Testament never mentions remaining single. Having children was a blessing of the covenant. But this also meant the Israelites experienced barrenness as a curse, which the anguish of Sarah, Rebekah, Rachel, Samson’s mother, and Hannah demonstrated.

God had promised Abraham a seed and a holy land. To have children was to participate in this project. Each family had a plot of ground as an inheritance in the promised land, and it passed along from one generation to another. Failing to procreate meant losing this divine inheritance (see Num. 27:1–11; 36) and being alienated from the redemptive project by which God would bring the Messiah from Abraham’s line.

Promised Seed Has Come

Like the Old Testament, the New Testament affirms natural-order sexual morality. It honors marriage and family, prohibits adultery and various extramarital relations, and advises most Christians to marry (see 1 Tim. 5:14). Jesus appeals to the creation order to defend the norm of lifelong, monogamous, heterosexual marriage (Matt. 19:4–9), and Paul appeals to the natural law when speaking against homosexual conduct (Rom. 1:18–27).

But the New Testament also speaks about sex and marriage both in ways the created order can’t account for and in ways that differ from the Old Testament. The Seed promised to Eve and Abraham has come (Gal. 3:16; Rev. 12), made atonement, entered the new creation, and made his people citizens of heaven and heirs of an unshakable kingdom (Phil. 3:20; Rom. 8:17; Heb. 12:28).

Without changing the basics of sexual morality, these great events put marriage and family in a new light. Three issues briefly illustrate.

1. Christ calls new-covenant Christians to deprioritize their natural families in relation to his kingdom, and even to be willing to give them up for his sake (Matt. 10:34–37; Luke 14:26).

As the new-covenant church spreads throughout the unbelieving world, conflict between family and Christ is now common. Yet for those who seek first the kingdom (Mark 10:29–30; cf. Matt. 19:29; Luke 18:29–30), Christ mercifully provides a new and more important family, that is, fellow Christians (see Mark 3:31–34). Christians are brothers, and the church is God’s “household” (Gal. 6:10; Eph. 2:19; 1 Tim. 3:15).

2. Remaining unmarried is valid and can even be a preferential option for some Christians (1 Cor. 7:6–9, 28–40).

Marriage, after all, is only for “this age” (Luke 20:34–35; see Matt. 22:29–32). Since all marriages end at death (Rom. 7:2) and no one marries in heaven, Christians will be unmarried in glory. Therefore, serving Christ now with undivided devotion as an unmarried citizen of heaven foreshadows the age to come (1 Cor. 7:32–35).

3. The New Testament never considers barrenness a curse for new-covenant believers.

Yes, Elizabeth regarded her barrenness as a curse (Luke 1:25), but she was still living under the old covenant. Because the promised Seed has come and secured the inheritance of God’s people, barren women no longer experience alienation from God’s redemptive project.

The fruitful-and-multiply theme drops out of the New Testament altogether, except as it applies to God’s Word and the Christian’s sanctified life (Col. 1:5–6, 10). The disappearance of this theme is now our blessing. It signals that Christ’s work is complete.

While Christians should honor marriage and family, we must remember that Jesus considered loyalty to family as one of the greatest stumbling blocks to discipleship.

The implications are numerous. While Christians should honor marriage and family, we must remember that Jesus considered loyalty to family as one of the greatest stumbling blocks to discipleship. Countless people still forsake their commitment to Christ for the sake of marrying an attractive unbeliever, retaining parental approval, or appeasing children.

Furthermore, contrary to the practice of some “family-friendly” churches, churches should honor rather than marginalize their unmarried members and encourage them in their Christian service. And while Christians are still grateful for their children, we must never consider infertility a sign of God’s curse under the new covenant.

Christians live in the overlap of the ages. As we await Christ’s return, may we live upright lives under this present creation order but never forget we’re already citizens of a new-creation kingdom.