1But false prophets also arose among the people, as false teachers will also be among you, who will secretly bring in destructive heresies, denying even the Master who bought them, bringing on themselves swift destruction. 2Many will follow their immoral ways, and as a result, the way of the truth will be maligned. 3In covetousness they will exploit you with deceptive words: whose sentence now from of old doesn’t linger, and their destruction will not slumber.
4For if God didn’t spare angels when they sinned, but cast them down to Tartarus, and committed them to pits of darkness to be reserved for judgment; 5and didn’t spare the ancient world, but preserved Noah with seven others, a preacher of righteousness, when he brought a flood on the world of the ungodly, 6and turning the cities of Sodom and Gomorrah into ashes, condemned them to destruction, having made them an example to those who would live in an ungodly way, 7and delivered righteous Lot, who was very distressed by the lustful life of the wicked 8(for that righteous man dwelling among them was tormented in his righteous soul from day to day with seeing and hearing lawless deeds), 9then the Lord knows how to deliver the godly out of temptation and to keep the unrighteous under punishment for the day of judgment, 10but chiefly those who walk after the flesh in the lust of defilement and despise authority. Daring, self-willed, they are not afraid to speak evil of dignitaries, 11whereas angels, though greater in might and power, don’t bring a slanderous judgment against them before the Lord. 12But these, as unreasoning creatures, born natural animals to be taken and destroyed, speaking evil in matters about which they are ignorant, will in their destroying surely be destroyed, 13receiving the wages of unrighteousness; people who count it pleasure to revel in the daytime, spots and defects, reveling in their deceit while they feast with you; 14having eyes full of adultery, and who can’t cease from sin, enticing unsettled souls, having a heart trained in greed, accursed children! 15Forsaking the right way, they went astray, having followed the way of Balaam the son of Beor, who loved the wages of wrongdoing; 16but he was rebuked for his own disobedience. A speechless donkey spoke with a man’s voice and stopped the madness of the prophet.
17These are wells without water, clouds driven by a storm, for whom the blackness of darkness has been reserved forever. 18For, uttering great swelling words of emptiness, they entice in the lusts of the flesh, by licentiousness, those who are indeed escaping from those who live in error; 19promising them liberty, while they themselves are bondservants of corruption; for a man is brought into bondage by whoever overcomes him.
20For if, after they have escaped the defilement of the world through the knowledge of the Lord and Savior Jesus Christ, they are again entangled in it and overcome, the last state has become worse for them than the first. 21For it would be better for them not to have known the way of righteousness, than after knowing it, to turn back from the holy commandment delivered to them. 22But it has happened to them according to the true proverb, “The dog turns to his own vomit again,” and “the sow that has washed to wallowing in the mire.”
"The oldest, and likely the most widely held, interpretation is that the “sons of God” are fallen angels (demons). This was the interpretation most favored in ancient Judaism and the early church (cf. 1 Pet. 3:19, 20; 2 Pet. 2:4; Jude 6). The phrase “sons of God” is clearly used elsewhere of angelic hosts in God’s heavenly court (cf. Job 1:6; 2:1; 38:7). Moreover, the narrator seems to contrast “man” and “the daughters of man” with the “sons of God” in Genesis 6:1, 2."
"This position is not without difficulties, however, the most substantial of which is the idea of fallen angels having physical relations with women. Scripture gives instances of angels engaging in human activities such as eating (Gen. 18:1, 2, 8; 19:1, 5), but surely sexual intercourse is a step beyond! Jesus makes a similar point in Matthew 22:30: “For in the resurrection they neither marry nor are given in marriage, but are like angels in heaven.” William F. Cook, Who Are the Sons of God in Genesis 6? Some of these church fathers were Justin Martyr, Eusebius, Clement of Alexandria, Origen, and Commodianus. Douglas et al. 2011, p. 1384
Most early church fathers in the first three centuries believed that the sons of God were angels who had unnatural sex with women and bore children. This perspective changed with St. Augustine of Hippo, who argued in the City of God that the sons of God were descendants of Seth.
The argument that Jesus taught that angels in heaven did not marry has no impact on the Genesis 6 passage since the angels in Gen 6, as accepted by Jude and Peter, were not unfallen angels in heaven but evil angels who were part of the fallen angels, or unfallen angels involved in human activity before the flood, who also fell. The ability to have sex and bear children appears to be a major argument against the "angel" view, but one must remember that angels in Gen 18 came in human form, along with Yahweh, ate food and drank, and had their feet washed. Moreover, in the New Testament, angels always appear in a male human form." See my article, Will We Eat and Drink in the Coming Kingdom of God? An Interpretation with Origen, Cerinthus, the Church Fathers, and the Literal Interpretation of the Scriptures on the Nature of the Millennial Kingdom.
6. And the angels who kept not their first estate but left their own habitation, he hath reserved in everlasting chains under darkness the judgment of the great day.
The strongest text that associates the sons of God in Genesis 6:1-4 is the Book of Enoch (6:11), referenced by the writer Jude in 1:6: "When the son of men had multiplied, in those days, beautiful and comely daughters were born to them. 2/ And the watchers, the sons of heaven, saw them and desired them. And they said to one another, "Come, let us choose for ourselves wives from the daughters of men, and let us beget children for ourselves."[1]
The ancients had many traditions of deities cast out from heaven. See notes on Genesis xi. 8. Jove, deceived by the goddess Ate, is represented by Homer as having cast her forth, forbidding her return to Olympus with an oath.
"From his ambrosial head, where perch'd she sat,
He snatched the fiery goddess of debate,
The dread, the irrevocable oath he swore,
The immortal seats should ne'er behold her more;
And whirl'd her headlong down, for ever driven
From bright Olympus and the starry heaven." Il 1. xix. v. 126
Jove declares that any deity who interferes in the strife between the Greeks and
Trojans—
"Far, oh far, from steep Olympus thrown,
Low in the dark Tartarean gulph shall groan,
With burning chains fixed to the brazen floors,
And lock'd by Hell's inexorable doors.''-Hom. ll, 1. xix v. v.3.
" With enduring chains
He bound Prometheus, train'd in shifting wiles,
With galling shackles fixing him aloft."-Hes. Theog. v. 521.
[1] George W. E. Nickelsburg and James C. VanderKam, 1 Enoch: A New Translation (Minneapolis: Fortress Press), p. 23.