John Chrysostom, on Gen 6:2

"Now, when the sons of God saw that the daughters of men were beautiful, they took wives for themselves from them all just as they were inclined." Let us study each expression of this statement closely so that nothing of what is hidden below the surface may pass us by. You see, there is need to make a careful study of this passage and confute the fanciful interpretations of those people whose every remark is made rashly - firstly, to repeat what they presume to say, and by demonstrating the absurdity of what is said by them to teach your good selves the true sense of Scripture so that you will not lend your ears idly to people uttering those blasphemies and presuming to speak in a way that brings their own persons into jeopardy. I mean, they claim that this remark is made not about human being but about angels; these (they say) he called sons of God. Let them demonstrate firstly where angels are called sons of God; they would not, however, be able to show this anywhere. While human beings are called sons of God, angels are nowhere so called. On the contrary, it speaks about angels in these terms: "He makes the winds his angels, fire and flame his ministers," whereas about human beings, "I said, You are gods," and again, "Sons have I begotten and raised," and again, "Israel my firstborn son" - but an angel is nowhere called son, or son of God. What in fact do they claim? To be sure, they really were angels, but because they fell into this lawless way, they lost their status...

Is it not a particular hallmark of folly to claim that angels descended to have intercourse with women, and that incorporeal nature of theirs was reduced to association with corporeal creatures? Or do you not hear the words of Christ about the being of angels, "At the resurrection they neither marry nor are given in marriage, but are like angels of God"? After all, it is not for that kind of incorporeal creature to ever feel the onset of desire. In response to these people we have to reach the same conclusion, that to admit this notion into one's mind is the height of absurdity.

We made the point before in teaching you that it is customary with Scripture to call human beings sons of God. So since these people took their origin from Seth and from his son named Enosh (the text, remember, saying, "He it was who hoped to invoke the name of the Lord God"), those descended from him in the future were called sons of God by Sacred Scripture for the reason of their imitation of the virtue of their ancestors up to his time. On the other hand, he gave the name sons of men to those born after Seth, the descendants of Cain and those taking their descent from him.