Having given this brief but sweet introduction, Jude dives immediately into his purpose for writing.  We receive at once a hint that he had communicated with these brethren before, for he speaks in the past tense of having once given diligence to write to them concerning the common salvation, to exhort them to earnestly contend for the faith which was once delivered to the saints.  An excellent purpose for a letter indeed!  And, surely, it is something very needful for all Christ’s churches in every generation.  We need faithful men constantly to remind us of the wonderful details of our salvation, teaching us concerning the electing love of the Father’s, the sacrificial love of Christ, Who died in our stead as a propitiation to God, and of the regenerating and sanctifying work of the Holy Spirit.   Constant emphasis on this salvation, which is common to all the chosen people of God, is positively necessary for the maintenance of spiritual health and strength in the churches.

But Jude wrote not only to refresh the souls of the believers by reminding them of the immense spiritual blessings which accrue to the household of God in salvation, but also to exhort them to contend earnestly for the faith.  Jude had no thought of a flippant “once saved always saved” notion which breeds laziness and indifference in the professor.  He was certainly no proponent of that damnable “carnal Christian” theory.  Though, as we will see at the conclusion of the epistle, he was firmly persuaded that the grace of God was able to keep His people from falling, Jude nevertheless understood at the same time that the Christian life is one of constant and unrelenting spiritual warfare, and that the enemies of the faith must be withstood and slain by the sword of the Spirit.  We may not rest on our laurels, and above all we may not be indifferent when false doctrine penetrates the church.  When people begin to deny the necessity of blood atonement, question the virgin birth or resurrection of Christ, deny the miracles, question the authority of Scripture, at the same time calling themselves Christians, we have no right to gloss over their errors out of “Christian love.”  No, we are to plant our feet squarely upon the infallible truth of God’s word, and not permit ourselves to be moved.  We may, surely, tolerate certain disagreements among brethren over interpretation of passages and issues which are not essential to our salvation.  But when the fundamentals of the faith are attacked, the Christian must contend earnestly.  When the virgin birth of Christ, His deity, the Trinity of persons in the Godhead, and such like fundamental doctrines are attacked, we cannot tolerate them out of Christian charity, but must assault their error with the truth of God’s word, and, if they do not relent, quickly excise them and their error from the body of the church, lest their word spreads and eats away like a canker.