Contend for the faith that was once for all entrusted to the saints. Jude 1:1-4

Jude 1:1-4
Salvation is good and shared, but more important matter is urge them to contend(爭辯) for the faith that was once for all entrusted to the saints.
Some godless men, who change the grace of our God into  a license for immorality and deny Jesus Christ out only Sovereign and Lord. They secretly slopped in among us.
The author of this letter is Jude, the younger brother of Jesus and James, now an old man. He was already thinking of writing, when alarming news of false teaching made him pen this short, vigorous letter with all speed.
Though he had wanted to write 'about the salvation we share'. Jude writes, instead, urging he Christians to hold fast to the truth. For 'certain men' have infiltrated the group and are now creating division by their false teaching. These men are so arrogant as to deny Christ. And Christian freedom has been turned into license.
Why?
Contend for the faith, for salvation could not be abused as immorality license and Jesus Christ is our center and foundation of truth.
Prevent the false Christians and hold fast to the truth.
How?
Trust our faith in Jesus Christ and careful to those who deny Jesus Christ and immorality men.