Jude 1

1 Jude, a servant of Jesus Christ and brother of James, To those who are called, beloved in God the Father and kept for Jesus Christ:

The name Jude is a variation of Judas, and Jesus had two disciples by that name. Judas Iscariot was the one who betrayed Jesus, but the second Judas, or Jude, was identified as "not Iscariot" (John 14:22; Acts 1:13).

In fact, Jude was the half-brother of Jesus and brother of James, leader of the first Jerusalem church. Jude does not identify himself as a brother of Jesus out of humility and reverence for Christ.

2 May mercy, peace, and love be multiplied to you.

3 Beloved, although I was very eager to write to you about our common salvation, I found it necessary to write appealing to you to contend for the faith that was once for all delivered to the saints.

Jude was eager to write to his readers about our salvation; but he changed his mind in order to urge them "to contend for the faith that was once for all delivered to the saints." This faith embodies the complete body of Christian doctrine taught by Christ, and later passed on to the apostles, and is now given to us in Scripture.

4 For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ.

Has anyone crept into your church that fits this description? False teachers and false Christians may not deny Christ with their lips, but they deny him in their actions (e.g. homosexuality) or they deny him with their false beliefs about God. Universalism, the belief that there is no hell and everyone, no matter who they are, will go to heaven after they die is becoming increasingly popular within Christendom. There are so many heretical beliefs that one could fill a book with them. Even John Stott stated he believed in annihilation another unbiblical belief, and he was recognised as "an evangelical Christian".

5 Now I want to remind you, although you once fully knew it, that Jesus, who saved a people out of the land of Egypt, afterward destroyed those who did not believe.

6 And the angels who did not stay within their own position of authority, but left their proper dwelling, he has kept in eternal chains under gloomy darkness until the judgment of the great day-

7 just as Sodom and Gomorrah and the surrounding cities, which likewise indulged in sexual immorality and pursued unnatural desire, serve as an example by undergoing a punishment of eternal fire.

I once heard a preacher, who open openly said that he believed in Liberal Theology, preach from the pulpit that God did not condem Sodom for its homosexuality but rather for its inhospitality, and that, in fact, it had nothing to do with sex at all. This idea is propagated by the so-called "Gay Theology" which is no theology at all, but the teaching of devils! This same preacher openly campaigned for our church denomination to recognise and even bless gay marriages - yes seriously! Anyway, this particular verse is biblical proof that he was trying to pull the wool over our eyes in his sermon. The Apostle Peter says Sodom "indulged in sexual immorality" and God judged them with "a punishment of eternal fire" (2Pet 2:7). Thus, it is written! Nuff said!

8 Yet in like manner these people also, relying on their dreams, defile the flesh, reject authority, and blaspheme the glorious ones.

Do we read the these words and gloss over them? What do they acutally mean? We should try and dig deeper:
relying on their dreams: Do you know self-professed Christians who go on about their dreamy, mystical, New-Age, or mystical experiences. Such things have no place in true Christianity, especially if such boasters ignore Scripture in their boasts.
defile the flesh: self-justified sexual immorality e.g. pornography, homosexuality, transgenderism etc.
reject authority: We Christians are supposed to submit to Christ. On this present earth, God has revealed his authority in the Bible, but there are actually people who call themselves Christians but disbelieve that the Bible is God's word. If so, they reject God's authority and are not Christians at all.
and blaspheme the glorious ones: They blaspheme the Father, the Son and the Holy Spirit.

9 But when the archangel Michael, contending with the devil, was disputing about the body of Moses, he did not presume to pronounce a blasphemous judgment, but said, "The Lord rebuke you."

Michael is also mentioned in Daniel 10:13, Daniel 12:1, and Revelation 12:7. The popular perception of an angel is unbiblical. The Greek word angelos which is a translation of the Hebrew word malak simply means messenger. Messengers from God appear in both the OT and NT, and rarely do they have wings. Rather they appear like men - never women - or children. The word malak can be used for human men too. The Messiah is called the "angel of the covenant" (umalak habbarit) in Malachi 1:1. That shows there's at least one verse in the Bible calling Christ an "angel".

Despite popular misconceptions, Gabriel, the only other named angel in the Bible, is not called an "archangel". It can be argued that the use of "arch" (as in the English word monarch) is an exclusive title. That is, there is only one archangel and he is Michael whose name means "He who is like God." Since no one is like God then Michael is himself God, or rather, one person of the Godhead i.e. the uncreated second person of the Trinity, who is God the Son, or Christ. If this theory is correct then Michael, the sole Archangel is none other than the Angel of the LORD (malak Yahweh) of the OT, who was the preincarnate Christ - the same angel who appeared to Joshua (Josh 5:15), calling himself "the commander of the army of the LORD" and demanded worship thus identifying himself as God. We are told Michael will lead the angels in the final fight against Satan and his (fallen) angels in Revelation 12:7.

10 But these people blaspheme all that they do not understand, and they are destroyed by all that they, like unreasoning animals, understand instinctively.

11 Woe to them! For they walked in the way of Cain and abandoned themselves for the sake of gain to Balaam's error and perished in Korah's rebellion.

Three OT people mentioned in one verse: Cain, Balaam, and Korah. We really need to know our OT or we won't understand what Jude is saying here.

Cain: was the first murderer in human history. He was murdered his brother, Abel, because he was jealous of the fact that God approved of Abel's righteousness Genesis 4.

Balaam: was a prophet, but rather than using his gift to speak God's word, he accepted bribes from Israel's enemies and tried to prophecy against Israel. God prevented him from doing so. Eventually, God sent the Angel of the LORD to kill him. God even caused Balaam's donkey to rebuke him Numbers 22.

Korah: was jealous of Moses being the leader of Israel, and gathered others in an attempted coup, despite the fact that it was God himself who had appointed Moses. God caused the ground to swallow him up along with all the rebels Numbers 16.

12 These are blemishes on your love feasts, as they feast with you without fear, looking after themselves; waterless clouds, swept along by winds; fruitless trees in late autumn, twice dead, uprooted;

13 wild waves of the sea, casting up the foam of their own shame; wandering stars, for whom the gloom of utter darkness has been reserved forever.

14 It was also about these that Enoch, the seventh from Adam, prophesied, saying, "Behold, the Lord came with ten thousands of his holy ones,

Enoch is explicitly stated to be "the seventh from Adam". This verse right here disproves all claims that there are gaps in the genealogy list between Adam and Enoch.

15 to execute judgment on all and to convict all the ungodly of all their deeds of ungodliness that they have committed in such an ungodly way, and of all the harsh things that ungodly sinners have spoken against him."

16 These are grumblers, malcontents, following their own sinful desires; they are loud-mouthed boasters, showing favoritism to gain advantage.

17 But you must remember, beloved, the predictions of the apostles of our Lord Jesus Christ.

18 They said to you, "In the last time there will be scoffers, following their own ungodly passions."

Scoffers also in 2Pet 3:3.

19 It is these who cause divisions, worldly people, devoid of the Spirit.

20 But you, beloved, build yourselves up in your most holy faith; pray in the Holy Spirit;

21 keep yourselves in the love of God, waiting for the mercy of our Lord Jesus Christ that leads to eternal life.

22 And have mercy on those who doubt;

23 save others by snatching them out of the fire; to others show mercy with fear, hating even the garment stained by the flesh.

24 Now to him who is able to keep you from stumbling and to present you blameless before the presence of his glory with great joy,

25 to the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever. Amen.

External links:
Summary of the Book of Jude https://www.gotquestions.org/Book-of-Jude.html
Who was Jude in the Bible? https://www.gotquestions.org/Jude-in-the-Bible.html