“Honor thy father and thy mother, that your days may be long in the land that the Lord your God is giving you. Thou shalt not commit adultery.” (Exodus 20:12&14)
God’s standards on human sexuality are treated in Scripture as the most important of all rules for relations among people. In the Old Testament, teaching against adultery is emphasized second only to teaching against idolatry. In the New Testament, both Christ and the apostles emphasized marital fidelity. Paul includes sexual sins in every one of his many lists of sins, and in most cases they head the list and receive the greatest emphasis. Why does the Bible view this relationship between the sexes as so important?
Sexual fidelity, more than most virtues, clearly demonstrates the purpose of law: man’s welfare. Human sexuality is one of God’s most delightful gifts. But the sordid record of human history and the anguish of personal experience highlight the basic reality that this joy is reserved for those who “follow the Manufacturer’s instructions.”
This outcome is not surprising because human nature was designed to reflect divine nature, and God’s law is simply his expressed will that people conform to the moral nature of God. This reflection of the divine nature is many-faceted. “Image” includes the moral nature of God—and therefore fidelity and purity—but it also includes the ability to think rationally, to create, to love and be loved, and to communicate. Among these characteristics of God-similarity may be included human sexuality: “So God created man in his own image, in the image of God he created him; male and female he created them” (Gen. 1:27). The grammatical structure of this sentence does not demand a direct link between the two ideas. All that is certain is that God created human beings in some way similar to himself, and that he created humans in two different models: male and female.
Some have built an entire doctrine on the mistaken notion that this verse defines “image” as the male/female characteristic. Though Scripture does not present this as the only or even the paramount element of likeness to God, some contemporary interpreters seem to hold that this is the chief meaning of “image.” “Image,” in this view, means that man is a being-in-fellowship, as in the Trinity, and that male/female fellowship is the highest and best variety of fellowship. Even though this verse does not prove such a thesis, I think we are warranted in finding here and elsewhere in Scripture the idea that the maleness and the femaleness and their relationship, in some mysterious way, reflect God’s own nature.
The truth is that Scripture nowhere defines “image” nor explains the concept. But certainly, since the Trinity is one, yet three, and the three are cemented in a relationship of loving commitment, we can see in the Godhead the ideal model for biblical marriage. Human marriage seems designed deliberately to reflect the eternal reality of the best of all relationships—that of the Father, the Son, and the Holy Spirit and of God’s relationship with us.
If marriage laws reflect the very nature of God and were expressly designed for man’s best interests, why are these standards the most often violated? Does anything demonstrate more clearly man’s independent, arrogant, foolish, perverse, blind, and demonic fallenness?
We devote throughout the year, more attention to the topic of sex, marriage, and the home for several reasons. In the first place, we have combined the consideration of two of the Ten Commandments (the fifth and seventh). Furthermore, this is the area of life that seems to be most under assault by the powers of evil. We seem most vulnerable here, and we must do all within our power to mobilize the forces of our biblical understanding, of our combined Christian commitment, and of the concerted action of correctly-thinking people to defend this basic building block of personal and social well-being.  What can you do to promote loving commitment in your own marriage or of those around you? How can you pray today for marriages you know and for those in your culture?
 Introduction to Biblical Ethics (IBE), Robertson McQuilkin, (2014), 219-220.