Cain’s Sister Became His Wife
17 And Cain had relations with his wife, and she conceived and gave birth to Enoch. Then Cain built a city and named it after his son Enoch.Genesis 4:17 BSB
Incest has a negative connotation because after its fulfillment, God made a law that prohibited anyone from participating in it.
9 You must not have sexual relations with your sister, either your father’s daughter or your mother’s daughter, whether she was born in the same home or elsewhere.Leviticus 18:9 BSB
The word incest wasn’t even known in the ancient world, especially in a negative light, until the 13th century in secular society. But in the Scriptures, God made it illegal in the time of the Israelites’ exodus from Egypt when God gave Moses the Law, as seen above.
Even Adam’s wife, Eve, came from his body (rib). Eve was part of Adam, which represented the relationship between Jesus Christ and the church through the indwelling of the Holy Spirit. You can even say that Eve was, in a sense, related to Adam as she was created from part of his body.
The Fulfillment Of The Law
The early relationship between brother and sister was to populate the earth. When its function or purpose reached its climax, God put a stop to it and made it sinful. That is no difference from the Law. Once Jesus Christ fulfilled the Law, it was no longer active in a believer’s life to continue to adhere to it. Whoever did or does continue to follow it has rejected Christ.
17 Do not think that I have come to abolish the Law or the Prophets. I have not come to abolish them, but to fulfill them.Matthew 5:17 BSB
2 Take notice: I, Paul, tell you that if you let yourselves be circumcised, Christ will be of no value to you at all. 3 Again I testify to every man who gets himself circumcised that he is obligated to obey the whole law. 4 You who are trying to be justified by the law have been severed from Christ; you have fallen away from grace.Galatians 5:2-4 BSB
I am not saying that we should disregard the Old Testament, but the parts that foreshadowed Christ like animal sacrifice, keeping special days, and abstaining from certain foods were fulfilled in Christ (Hebrews 9:8-28, Colossians 2:16-17). The moral Law was and will always be active. It was before the Law of Moses and will continue to be a Law that a Christian has to live by, not to attain righteousness, but as evidence of the indwelling of the Holy Spirit. The Word of God sums it up in two commandments:
37 Jesus declared, “ ‘Love the Lord your God with all your heart and with all your soul and with all your mind.’ 38 This is the first and greatest commandment. 39 And the second is like it: ‘Love your neighbor as yourself.’ 40 All the Law and the Prophets hang on these two commandments.”Matthew 22:37-40 BSB
The Moral Law has to do with your relationship between you and God and between your behavior in how you treat other people.
In conclusion, the notion of incest was not known when men started to multiply on the face of the earth. God stopped the relationship between brothers and sisters after the earth has reached the population that God desired and He put a stop to it because it accomplished its purpose.
The Lord puts laws that are to be kept and followed and other laws have a limit that after it is fulfilled it stops from being active. God does not condone incest. The word “incest” is a negative word. It became that after God said it must not be practiced any longer. If God had never prohibited it, today people would have seen it as the norm. Eventually, what God deems to be sinful, the world will accept as good.
For example, homosexuality from the start was condemned by God. But the world now is deeming it as moral and not only that, but the world is also drifting to incest as being okay. Once you allow a twisted sin to be normal, the rest will follow.
To learn more on what God thinks about homosexuality click on this link: Category: Homosexuality
If society accepts men and men relations, eventually, it will include incestuous relationships and who will stand against it if the moral of society, which is not absolute, makes it moral? In the Book of Judges, society declined because they abandoned God and did whatever seemed right in their own eyes and practiced homosexuality, incest, and other sinful lifestyles (Leviticus 18:24-25, Judges 2:10-13; 21:25). That is exactly what is happening in today’s world.