The seventh commandment is:
Thou shalt not commit adultery (Exodus 20:14).
Thus, this commandment regulates behavior where married people are involved. But why did God not choose to make this commandment “Thou shalt not commit fornication”? Would that not have covered much more ground?
In a Christian marriage, there is an agreeing with God, a joining together of man and woman. God joins them together. The two have become one flesh. And “What therefore God hath joined together, let not man put asunder” (Matthew 19:6). Adultery is a separation of what God has joined together. Fornication, in contrast, is a merely temporary, immoral, selfish event between two persons whom God has (obviously) not joined together.
The marriage bond is sacred; to violate it is a base betrayal. Marriage is presented in Scripture as a model or illustration of the union between Christ and His church (Ephesians 5). Whenever the marriage covenant is violated, that model is sharply distorted.
One coming from an anarchist perspective might immediately pursue this question in terms of property rights violation. The man and the woman are married. Therefore, The man owns the woman and for someone else to use her thus is a violation of his property rights. Actually, that would be backwards. Marriage means giving yourself to someone else. Marriage contains a surrender of certain of your “rights” to your partner, and likewise in return (1 Corinthians 7:3, 4). Thus, for a husband to engage in sexual relations with a woman other than his wife, is for him to violate not his own, as it were, but his wives “property rights.”
God is against sexual immorality no matter its form, but in the Ten Commandments chose to highlight adultery. Adultery can break a union, shatter lives. Fornication leaves behind its own evil and distinct trail of woes, but not is not the breaking of a divinely sanctioned union.
It may be well to pause here for a moment and recognize that this commandment, like the fifth and the tenth, recognizes gender differences. The current trendiness of homosexuality in the culture has led to a frantic desire on the part of some for the state to recognize the legitimacy of homosexual “marriages.” The issue, as stated, is one of justice.
Here, we see exactly why the state should not stick its large nose into the question of marriage. It has no business licensing or legitimizing them. Christian marriage is a religious institution. If non-Christian parties wish to enter into a social contract of whatever name or arrangement between consenting adults, that is no concern of anyone but themselves.
The Christian can stand aside and recognize that something is very wrong there and even encourage such parties to reconsider their behavior. It is rather clear from Scripture, although we will not argue the case here, that homosexual relationships are chosen, immoral, sinful behavior. By definition, a man cannot marry a man, nor a woman a woman; the Bible is unambiguous in presenting Christian marriage as properly entered into between man and woman.
Because the divine image is reflected in the union of man and woman (Ephesians 5:22-33), a union of man with man or woman with woman is an inherent distortion of God’s purpose.
Having said all this, homosexuals should try to understand that it is not offered in judgment. The homosexual “union” is akin to fornication. God loves the fornicator and the adulterer both, even as He finds their immoral behavior revolting. The state has no business regulating marriage. Whatever agreement consenting adults wish to enter into between themselves is their own business. The state should leave it alone. The state, whether by statute or constitution should keep out of these matters and let adults choose for themselves.