Genesis 6:1 & 2
"When men began to increase in number on the earth and daughters were born to them, the sons of God saw that the daughters of men were beautiful, and they married any of them they chose." NIV translation
At first glance, this seems good as man was designed to be married to a woman. To fully understand this chapter, we need to look at the meaning of "sons of God" and "daughters of men". Some have said that "sons of God" refers to angels but that is not correct because good angels would not sin and bad angels would not be called "sons of God" (they are called demons). The phrase is actually talking about the descendants of Adam through Seth which, as we saw in chapter five, were the line of godly men. The phrase "daughters of men" refers to the descendants of Adam through Cain which, as we saw in chapter four, were worldly men. We see that the godly men of Seth were tempted by the beauty of the daughters of the worldly men of Cain and they married them. We notice that they "chose" to marry them which is the opposite of the way God designed marriage to happen. As we saw in chapter two, God's plan for marriage was that He would create a woman for a man and He would present the woman to the man (all the man had to do was to wait on God and accept the gift of the woman that was created specifically for him). In this short passage, we see the struggle that continues in the world today which is the inner struggle of man between the call of God (spirit) and the call of the world (flesh).