"Beloved,
while I was very diligent to write to you concerning our common salvation, I
found it necessary to write to you exhorting you to contend earnestly for the
faith which was once for all delivered to the saints."
Jude 1:3
What Jude wrote to believers is very instructive, exhorting believers to contend earnestly for the faith. It is telling he did not direct believers to contend with heretics or those who seek to turn people away from the truth--though at times it may be required. In following verses Jude provided examples of ungodly conduct and apostasy we are equipped through scripture to discern. But "destroying" people is not the target of any action we take because our aim is to positive, not negative: we are to contend for the faith. Our primary purpose in our response is to promote Jesus Christ by example and deed above denouncing false doctrine and those who teach them. Arguments which rise up contrary to Christ should be cast down and unrepentant heretics and apostates cast out, but these conflicts are secondary in our intent to uphold the Gospel and the Word of God.
Paul informed believers their battle was not against flesh and blood but against principalities, powers, and rulers of darkness. This spiritual battle is played out in the real world and involves other people, and this battle that is the LORD's has been declared a victory by Jesus Christ. The exhortation of Jude is all believers are to "contend earnestly for the faith" which was delivered to us once for all. The phrase "earnestly contend" comes from a Greek word that means to struggle for, the word from which the English word "agonise" is derived. In a world darkened with sin to live for God will be a struggle yet can be accomplished by the grace of God in the power of the Holy Spirit. Earnestly contending for the faith is more than debating doctrine but in living in the way which pleases God.
It is one thing to be able to recognise what is right and wrong but another thing altogether to walk accordingly. Paul continued on the subject of why they ought to contend earnestly in Jude 1:4: "For certain men have crept in unnoticed, who long ago were marked out for this condemnation, ungodly men, who turn the grace of our God into lewdness and deny the only Lord God and our Lord Jesus Christ." Paul then provided examples of the ungodly sort of men who had infiltrated the church who turned the grace of God into license to sin and denied Christ by their lives marked with unbelief, abuse of authority, sexual immorality, hate, greed, hypocrisy, complaining, and pride. Our agonising is not primarily to ferret out these things from the lives of others but to take an honest look at ourselves, repent of our sins, and contend earnestly for the faith.
Those who have been born again by grace through faith in Jesus Christ have the Holy Spirit the infiltrators do not have. A fig tree will produce figs, and a child of God will bear a growing resemblance to Jesus Christ in faith, love, and obedience to God. If our lives resemble those negative examples Jude provided, we work to undermine the truth of the Gospel rather than adorning it. Paul laboured with singular focus to this end as he wrote in Philippians 3:14, "I press toward the goal for the prize of the upward call of God in Christ Jesus." Jesus and the Word of God has delivered to us doctrine that is pure and true, and Jesus set the bar infinitely high in living up to it. As His faithful followers, we ought to contend earnestly for the faith.