And the angels who kept not their first estate, but left their own habitation, he has reserved in everlasting chains under darkness unto the judgment of the great day.
All Commentaries on Jude 1:6 Go To Jude 1
Aquinas Study Bible
AD 2017
The idea conveyed here, is the same with that expressed in 2 Peter 2:4. Although the words of this passage would appear to afford grounds for the opinion that the demons are confined to hell, it is, however, the far more probable opinion, that they were first hurled into hell, and that some of them were by divine dispensation, as St. Thomas Aquinas (Sum Theo 3.89.8) expresses it, allowed to come forth to tempt and carry out war against mankind. (Bishop John McEvilly) under darkness and everlasting chains: perhaps this is a specific place called TARTARUS. (John Litteral)