For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into licentiousness, and denying the only Lord God, and our Lord Jesus Christ.
All Commentaries on Jude 1:4 Go To Jude 1
Aquinas Study Bible
AD 2017
secretly entered in: They entered the midst under the disguise of religion and crept like wolves into the Lord’s sheepfold. They had the appearance of godliness, though they were the enemies of genuine godliness. (Erasmus)
who were written long ago: Jude means that their condemnation was predestined, for even the betrayal of Judas had been foretold. (Andreas of Caesarea)