Genesis 6 begins with a much debated passage:
Now it came to pass, when men began to multiply on the face of the earth, and daughters were born to them, 2 that the sons of God saw the daughters of men, that they were beautiful; and they took wives for themselves of all whom they chose.Genesis 6:1-2
Some believe this passage is speaking of human women sleeping with evil angels or evil spirits. Some believe this passage is speaking of women becoming wives and sleeping with men of renown, kings and princes, etc. Others believe this is speaking of men from the line of Seth taking for themselves wives from the line of Cain.
I go with the latter. The latter is the least supported position amongst modern commentators and even ancient Jewish writers such as Philo and Josephus (they supported the angel and humans intercourse theory).
Why do I choose the idea of Sethites mingling with Cainites, because to me it fits in with the rest of the narrative of the Old Testament. As one will discover in later books God consistently warns God’s people not to take wives from those that are not followers of the one true God. And in multiple places in scripture when this does happen, wickedness flourishes.
I believe Genesis 6 is the first time God has chosen to teach the “unequally yoked” concept of 2nd Corinthians 6.
Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness? 15 And what accord has Christ with Belial? Or what part has a believer with an unbeliever?2 Corinthians 6:14, 15
Marriage to someone that does not hold the same faith as you, (this does not mean they belong to the same denomination–a committed Adventist marrying a uncommitted Adventist or a committed Baptist marrying an uncommitted Baptist, is still being unequally yoked) is a path that often leads to deterioration in ones home, ones morals, and even as we see here in Genesis 6 society.
Then the Lord saw that the wickedness of man was great in the earth, and that every intent of the thoughts of his heart was only evil continually. 6 And the Lordwas sorry that He had made man on the earth, and He was grieved in His heart.Genesis 6:5,6
There are many reasons evil spreads in the world, but in the context of Genesis 6 it is firmly rooted in the relationships ungodly marriage relationships being developed in society.