Theophylact of Ohrid, on Jude 1:6

“And the angels who kept not their principality, but forsook their own habitation, he hath reserved under darkness in everlasting chains, unto the judgment of the great day.”

“And those who, having received the honor of angelic dignity, through negligence did not remain in their original state, but cast off the heavenly manner of life given to them by grace, God has hidden away in punishment for the judgment, that is, for the condemnation, of the great day; for this is what the word "keeps" means. Therefore the Lord also says: "Depart into the fire prepared for the devil and his angels" (Matt. 25:41).”

Imported from an open dataset — not yet checked against the printed edition.