Matthew Poole and continuators on Genesis 6:1

1. AND it came to pass when men began to multiply on the face of the Earth, and Daughters were born unto them .

(i. e.) Wicked men the posterity of Cain, as appears from the following verse: Who are here called men, and the Sons of men, by way of contempt, and of distinction, meer men, such as had only the natures and qualities of corrupt men, without the image of God.

To wit more than ordinarily, or more than the Sons of God, because they practised Polygamy after the example of their Predecessor, the ungodly Lamech, Gen. 4. 19.

So doubtless were Sons also; but their Daughters are here mentioned as one principal occasion of the sin noted in the next verse and of the following deluge.