When man began to multiply on the face of the land and daughters were born to them,
1. And it came to pass , when men began to multiply . Moses, having enumerated in order, ten patriarchs, with whom the worship of God remained pure, now relates, that their families also were corrupted. But this narration must be traced to an earlier period than the five hundredth year of Noah.
The curse of numbers: God's blessing on multiplied mankind became a curse when corruption abused it. Sin is a spreading leprosy, most destructive where sinners crowd together; the multitude of offenders emboldens men. But the greater wickedness here is mixed marriage: the professors of religion, the posterity of Seth, bound themselves to the profane daughters of Cain's line, abandoning their separation unto God.
AI summary
Commenting on Genesis 6:1-2
And it came to pass, when men began to multiply upon the face of the earth,.... Either mankind in general, or rather the posterity of Cain, who were mere natural men, such as they were when born into the world, and as brought up in it, destitute of the grace of God, and of the knowledge and fear of him; and who in proportion much...