Jude 1:1 "Jude, the servant of Jesus Christ, and brother of James, to them that are sanctified by God the Father, and preserved in Jesus Christ, and called:"

Jude identifies himself in two ways.  As the servant of Jesus and as the brother of James.  He was authentic.  He knew the truth and was getting ready to reaffirm it with the people to whom he was writing.

Note the order of the words I underlined.  You must be sanctified by the blood of Christ before you can be preserved for all eternity.  And then you are called.   Paul said in Rom. 8:28 "And we know that all things work together for good to the that love God, to them who are the called according to his purpose."  Sometimes you hear people say, "All things work together for good."  But that is only true if   you love God.  And if you are called--according to His purpose.  Not according to your purpose.

Jude was recognizing that the people to whom he was writing loved God.  They were living their lives according to God's purpose.  Because of this he continued in verse two by giving them a personal blessing:  "Mercy to you and peace, and love, be multiplied."  And then in verse three, he calls them "Beloved".  Jude loved these people.

Jude 1:3 "Beloved, when I gave all diligence to write to you of the common salvation, it was needful for me to write to you, and exhort  you that you should earnestly contend for the faith which was once delivered to the saints."

Jude is about to tell them that they have a war on their hands.  He is going to tell them how to identify false prophets.  This is a very important letter.  It gives us an outline of what will happen to those who mess around with God's plan of salvation by grace.