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 1)
The word “preserved” gives us the key to the Book of Jude which presents the apostasy as it is presented nowhere else in Scripture. But Jude doesn’t write just to frighten the daylights out of us. He gives us this background in order that he might give assurance in days of apostasy. He uses the word “keep” four times, which is what the word “preserve” means. They are kept in Jesus Christ — God is the one who keeps them.
In the physical world there are two ways of preserving food. One is with vinegar, and the other is with sugar. There are many saints in our day who I think are preserved, all right, but they are preserved in vinegar — that is, they act that way. They have a vinegar disposition. But even those who seem to be preserved in vinegar are preserved by God’s grace, which preserves or keeps them. The apostle John tells us in Revelation 12:11 that “…they overcame [Satan] by the blood of the Lamb…”, and that is the only way believers are going to make it through the Great Tribulation. And that is the only way we are going to overcome — by the blood of the Lamb. There is no merit or power in us to overcome the Evil One.
The Lord Jesus Himself gave an illustration when He said, “My sheep hear my voice, and I know them, and they follow me: and I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father’s hand” (John 10:27-29). Now if a sheep is kept in safety, it is no credit to the sheep. A sheep cannot defend itself. It doesn’t have sharp fangs and claws to fight its enemy. Neither can it run. A sheep is helpless. When one of God’s sheep says that he knows he is saved, he is not boasting of his own merit; he is boasting of his Shepherd. My friend, if you are saying that you are not sure of your salvation, you really are reflecting upon your Shepherd, because He says that He can keep you. He says that no created thing is able to take you out of His Father’s hand. It is not a question of whether or not you can hold on to Him. It is a question of His holding on to you. He says that He can, and it is a matter of your trusting Him.
You see, salvation rests upon the Word of God. It is up to you whether you will believe Him or not. Your assurance of salvation rests upon that, because He has made it very clear that you have a sure salvation. Here in Jude we are presented with the dark days of apostasy, and God still says that He is able to keep His own.
—From Edited Messages on Jude by J. Vernon McGee