INTRODUCTION TO THE LETTER FROM JUDE
From Jude. the brother of James. From the earliest times, Jude has beep identified as the Lord's brother. Neither he nor his brother James mention the fact that they are the Lord's brothers in the flesh, nor would we expect them to do so, since it would have been out of harmony with the spirit of humility. He did not believe in Jesus during the public ministry (John 7:5), but was one of the group in the upstairs room (Acts 1:14) which shows he had become a believer by that time, and he and his wife traveled among the churches (1 Corinthians 9:5).
No one can say for sure just when Jude wrote his Letter. Nor can anyone say for sure whether Jude wrote before or after the Second Letter from Peter, which is very similar. J.W. Roberts thinks it dates from 68 A.D., which would put it after Second Peter. Jude had probably read Peter's Second Letter before writing this. Jude's Letter was slower to be accepted, possibly because it is more specialized and may have had a smaller circulation.
Some people saw Christianity as a way to get rich. Compare 1 Timothy 6:3-5; Acts 8:9-19; Romans 16:17-18. These had no love for truth, and so to get a following, they taught that what Paul said about faith meant that God would not credit sin to a believer. They said: "The sinful actions of men are decreed by God, therefore He will not punish the one who continues to sin." Compare notes on Revelation 2:14; Revelation 2:20. Jude writes to show that God has already punished sin, and that He will continue to do so!
Jude and Peter write on the same subject, probably to emphasize that they, as "apostles of circumcision," oppose these false ideas and false teachers! See the Introduction to the Letter from James.