The reason for this letter

^3-4 I fully intended, dear friends, to write to you about our common salvation, but I feel compelled to make my letter to you an earnest appeal to put up a real fight for the faith which has been once and for all committed to those who belong to Christ. For there are men who have surreptitiously entered the Church but who have for a long time been heading straight for the condemnation I shall plainly give them. They have no real reverence for God, and they abuse his grace as an opportunity for immorality. They will not recognise the only master, Jesus Christ our Lord.

Past history warns us that the unfaithful have mingled with the faithful

^5-9 I want to remind you of something that you really know already: and although the Lord saved all the people from the land of Egypt, yet afterwards he brought to their downfall those who would not trust him. And the very angels who failed in their high duties and abandoned their proper sphere have been deprived by God of both light and liberty until the judgment of the great day. Sodom and Gomorrah and the adjacent cities who, in the same way as these men today, gave themselves up to sexual immorality and perversion, stand in their punishment as a permanent warning of the fire of judgment. Yet these men are defiling their bodies by their filthy fantasies in just the same way; they show utter contempt for authority and make a jest of the heavenly glories. But I would remind you that even the archangel Michael when he was contending with the devil in the dispute over the body of Moses did not dare to condemn him with mockery. He simply said, the Lord rebuke you!