The subject of this epistle is apostasy. Apostasy is shown to be wilful return to ungodliness. Two classes are dealt with: those who "kept not," and are therefore "kept"; and those who "keep themselves," and are "kept from stumbling."
The faith was in peril, and Jude wrote urging that they should contend earnestly for the faith. The faith for which he pleaded was a life of loyalty to the Lord. The danger was created by the presence and influence of certain men who were making the grace of God an occasion for lasciviousness.
Three illustrations were given of the evil results of apostasy, those of Israel, angels, and the cities of the plain. The fundamental wrong of the men referred to was insubordination: they were "setting at nought dominion, and railing at dignitaries." The influence of such men is like that of Cain, hatred and murder; of Balaam, seduction and lying; of Korah, envy and rebellion. In a passage full of fiery force, Jude denounced the evil of these ungodly men.
The subject of the h e attitude of believers in face of all these perils is dealt with. First, there is to be recognition of the danger. It has two distinguishing marks. The first is that their influence is that "they make separations," and the second is that their temper is sensual, not spiritual. In the presence of these perils it is important that believers should "keep yourselves in the love of God." This is to be done by building on faith, praying in the Spirit, and looking for mercy.
There is a relative duty. "On some have mercy," that is, those in doubt. "Some save," that is, probably, such as had been snared. These are to be snatched from the fire. "On some have mercy with fear," refers possibly to the Libertines themselves.
The epistle closes with a glorious doxology which ascribes to God the Saviour all honor for that He is able to accomplish the salvation of His trusting ones in two ways, which are all-inclusive: as to continuity, "able to guard you from stumbling"; and as to consummation, "to set you before the presence of His glory."