The "beloved" are those who are loved of God, God's adopted children. Jude wrote this letter at a time when he "was very diligent to write concerning our common salvation". By "very diligent" he means "hastening": he was in a hurry to write on some aspect of our salvation, which could have been on redemption, on the person of Christ, on sanctification, or any number of themes.
Regarding common salvation, it is curious that the New Testament was written in the days of the apostles in common Greek (the same word translated common) rather than classical Greek or Hebrew, so it could be understood by everyone all over the Roman Empire.
Whatever Jude was hastening to write had to be put aside because constraint was laid upon him to write on something else: it is implied that the Holy Spirit forced him to change the whole content of his message. The new content was to urge those receiving the letter to fight vigorously for what they had originally been taught, because of impending apostasy.
Apostasy is a departure from the apostles' teaching. It can now be perceived to have been just a little cloud in those days, but has become a formidable storm that fills the land in our days. Many of the things mentioned in this letter are now taking place.
In order to combat apostasy, it is necessary to fight vigorously, the words being "to contend earnestly" or "with intensity and determination". This does not mean "to be contentious", because we read : "And a servant of the Lord must not quarrel but be gentle to all, able to teach, patient, in humility correcting those who are in opposition, if God perhaps will grant them repentance, so that they may know the truth, and that they may come to their senses and escape the snare of the devil, having been taken captive by him to do his will." (2 Timothy 2:24-26). The word contend, as Jude uses it, has in it the idea of agony (epagonizesthai), suffering for.
We are to contend, or defend, and even suffer for the great teachings of Christ and His apostles which were once delivered to the saints, the believers in their time. "The faith" is the body of truth given once for all, which we find in the Bible.
In the Book of Acts it is called the apostles' doctrine: "they continued steadfastly in the apostles' doctrine and fellowship, in the breaking of bread, and in prayers" (Acts 2:42). The apostles' doctrine is the first thing mentioned, and that is the place it should take in all God's churches.
We are told in Ephesians 4:15 to speak the truth in love. We are also to be ready to give an answer to anyone who asks us, in meekness and fear. A believer should not have a short fuse and become angry when someone differs with him.
Jude sounds an alarm because something is happening to the church: certain men have slipped in secretly, as if by a side door, unnoticed. This is the way the apostates have always come into the church, and how they are able to take over a church. They "come in the side door" professing one thing and believing another. They do not come in the front door, that is, they do not declare their doctrinal position.
Two things are said about them:
they long ago were marked out for this condemnation: meaning that other writers had sounded the warning about apostates such as them.
they are ungodly men, who turn the grace of our God into lewdness and deny the only Lord God and our Lord Jesus Christ.
Scripture has warned about them. For instance, Paul wrote to the Corinthians: "For such are false apostles, deceitful workers, transforming themselves into apostles of Christ. And no wonder! For Satan himself transforms himself into an angel of light. Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works" (2 Corinthians 11:13-15).
The Greek expression translated "transforming themselves" in this verse means "the act of an individual who is changing his outward expression by assuming an expression put on from the outside." Paul also warned Timothy: "having a form of godliness but denying its power. And from such people turn away! For of this sort are those who creep into households and make captives of gullible women loaded down with sins, led away by various lusts" (2 Timothy 3:5-6). They are like chameleons. It is a method of Satan, the most deceitful in the world.
Over the years many strong, outstanding churches have been falling into the hands of liberalism by this method. Others have been taken over by false ("godless") teachers who "have secretly slipped in" and are twisting the Bible's teachings to justify their own opinions, philosophy, lifestyle, and behaviour. In doing this, they may gain temporary freedom to do as they wish, but they will discover that in distorting Scripture they are playing with fire. God will judge them for excusing, tolerating, and promoting sin.
Paul repeatedly warned of the apostates. The last time he went by Ephesus, at his last visit with the Ephesian elders, he gave this warning: "For I know this, that after my departure savage wolves will come in among you, not sparing the flock. Also from among yourselves men will rise up, speaking perverse things, to draw away the disciples after themselves. Therefore watch, and remember that for three years I did not cease to warn everyone night and day with tears" (Acts 20:29-31).
The "ungodly turn the grace of our God into lewdness" or immorality. The apostle Paul warned the Galatian believers about the danger of turning the grace of God into license to live any way they pleased. "For, brethren, ye have been called unto liberty; only use not liberty for an occasion to the flesh, but by love serve one another" (Galatians 5:13).
Some apostates today have thrown overboard all of the great precepts of Scripture concerning morality, and they call it the "new morality". Many first-century teachers maintained that Christians could do whatever they liked as they were no longer under the law. Paul refuted this false teaching in Romans 6:1-23.
Jude was contending with Gnosticism. It taught that the body was essentially evil, that all matter was evil, and that the spirit alone was good. The conclusion was that it didn't matter what a man did with his body. He was free to satisfy the lusts of the body, and proudly to flout immorality publicly. That was a perversion of grace. The same ideas have sprung up again today in the "new morality".
There have been many "movements" among churches, but any that deny the deity of Jesus Christ must be ruled out immediately. Peter prophesied: "there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Lord who bought them, and bring on themselves swift destruction" (2 Peter 2:1). This was the other facet of Gnosticism, which denied that our Lord Jesus Christ was true God and true Man. It is the mark of an antichrist: John calls such people antichrists in his epistle. It is always the spirit of antichrist which denies the Lord Jesus Christ.
They can, and often do, hide their denial of the deity of Christ by giving the impression that they actually believe in Him as the Saviour of the world. But what a person truly believes will show up in how he or she behaves. Those who minimise the wickedness of sin, saying that how they live has little to do with their faith, and wilfully behave in a manner unworthy of a son of God are, in effect, denying the only Lord God and our Lord Jesus Christ.
Some people avoid studying the Bible because they think it is dry and boring. Those who refuse to learn from it, however, are susceptible to false teaching because they are not fully grounded in God's truth. We must understand the basic doctrines of our faith so that we can recognise false doctrines and prevent wrong teaching from undermining our faith and hurting others.
3 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
.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.