The following is adapted from the commentaries of Ray Stedman, available as a free resource at the Blue Letter Bible website.
Now to him who is able to keep you from falling and to present you without blemish before the presence of his glory with rejoicing, to the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and for ever. Amen. (Jude 24,25)
This doxology falls into three divisions.
“Now to him who is able to keep you from falling” indicates the potential in the Christian life. It does not say “Now to him who does keep you from falling,” because God does not always keep us from falling. He is able to, Jude says, but he does not always do it. We need to fall sometimes; some of us will not learn any other way. If we were not so thick-headed and stubborn, and if we would obey him, he would keep us from falling. In that sense, we never need to fall.
But even when we do fall, he is able “to present us without blemish before the presence of his glory.” The word translated “without blemish,” is the word “anomas,” which means “apart from the law.” He has so completely dealt with us that even our falls have already been handled in Christ. Therefore, after we have learned the painful lesson of it, he is free to wipe it out of the record, and to present us faultless before his glory!
And this will be done, he says, with rejoicing. That means we will have had a part in this too. We are also involved in the process, and when we get where we’re going, we can say, “Hallelujah! Thank God, I’ve won!” As Paul says, “I have finished the race. I have kept the faith. Henceforth there is laid up for me the crown of righteousness.” (2 Tim. 4:7, 8)
Then there is the final recognition of the only God, our Savior, the Lord Jesus Christ. To him be “glory, majesty, dominion, and authority before all time and now and for ever.” That takes in everything, does it not? From the beginning, through the present to the eternal future, he is the One around whom the universe itself gathers.