St. Jude, who wrote this Epistle, was one of the twelve Apostles and
brother to St. James the Less. The time it was written is uncertain:
only it may be inferred from verse 17 that few or none of the Apostles
were then living, except St. John. He inveighs against the heresies and
wicked practices of the Simonians, Nicolaites, and Gnostics, etc.,
describing them and their leaders by strong epithets and similes, He
exhorts the faithful to contend earnestly for the faith first delivered
to them and to beware of heretics.