Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
The following commentary covers Chapters 6, 7, and 8.
Finally we find power and force here below, the result, of the sons of God not keeping their first estate, of apostasy; and God executes judgment instead of any longer pleading with men by the testimony of His Spirit in grace, which has its allotted term. The obedience of faith is the security of the warned remnant; but the principle of degeneracy worked on in spite of the testimony, and worked on the accomplishment of the testimony it despised. Man grew worse and worse, and God's creation was utterly defiled and filled with violence, the two universal characters of active will out of God. As regards man, it was now brought out, when he was left to himself (for before the flood, save gracious testimony, he was so left), that every thought of his heart was only evil continually. God creates and destroys; He calls and repents not. Creation was utterly corrupted, and God destroys it wherever the breath of life is. The testimony of these things is gone out everywhere among the heathen. We have here the exact though brief account of them, so far as needed to shew what man was and is, and God's ways with him.
In the midst of the ruin and judgment God points out the way of salvation through the judgment. The remnant taught of God profit by it. The flood is brought upon the world of the ungodly. Up to this, though the seed of the woman had been promised, sacrifice brought in, and testimony given, there were no special dealings of God with man. It was man walking before God in wickedness, no calling out, no law, no judgment. The world, man, was judged (save Noah and his family) and its deeds were hidden under an overwhelming flood. The judgment of God is accomplished; but He remembers His mercy.