Who are the “sons of God” and the “daughters of man,” and what kind of relationship is being described here? While some Bible scholars believe the “sons of God” are fallen angels who somehow become physically intimate with human beings, I think the better interpretation is that this passage is describing how the godly descendants of Seth intermarry with the ungodly descendants of Cain.
Here’s what Dr. W.A. Criswell said about it in his “Scarlet Thread” sermon: “Seth was a man of God; and Cain, driven out from the presence of the Lord, was a blasphemer. And then you have the progeny of those two: the line of Cain and the line of Seth, the children of God… Then in the sixth chapter of Genesis a tragic thing came to pass. The sons of God, the children of Seth, looked out into that world and they liked the glamour of the nightlife. And they liked the drunken orgies of the world. And they turned aside from their separateness and their dedication and their holiness, and they began to marry into the families of the sons of Cain. And God looked upon them, and His children had forsaken His altars and forsaken their devotion and had forgotten their consecration, and the whole earth was filled with violence and evil and iniquity… The children of God began to marry in the line of Cain, and the earth was filled with violence and blood and murder and blasphemy.”
What truth of the Gospel does this reveal to us? We all go our own way. We all live in a way that brings God’s condemnation and judgment upon ourselves. We need God to save us because we are lost. We need a Savior!