The wonderful change wrought in believers by the outpouring of the Holy Spirit is very noticeable, especially to the student of the Greek Testament. Strong words not found in the Old Testament, nor in the four Gospels, are either invented by the apostles or borrowed from classical Greek, to convey an adequate conception of the heavenly glory which has come into earthen vessels.
One such word, ἄπταιστος (aptaistos), "from falling," St. Jude uses in that remarkable ascription with which this brief epistle concludes (Jude 24). The R. V. reads. "Now unto him who is able to guard you from stumbling." This is more difficult than the K. J. V. inasmuch as the unsteady walker is more prone to stumble than to fall. The indwelling Spirit in his fullness can save even from stumbling.
Of course this does not signify intellectual mistakes. It is salvation from moral failures, however slight. Hence the Vulgate, the supreme standard in the Roman Catholic Church, has sine peccato, "without sin." This is the real significance of this adjective. Christ has sent down from heaven a personal guide, who is able to keep every Christian from the commission of sin. Let every doubter try it for himself. Satan is very busy in keeping in circulation the falsehood that freedom from sin is impracticable and impossible in this world. He who believes this lie will continue to commit sin. He will stupefy his own conscience with the idea that sin is inevitable. Soon he will begin to fight against the scriptural doctrine, "Whosoever is born of God doth not commit sin." There is no doctrine that the devil more cordially hates than the possibility of holiness perfected this side of the grave. When he gets a Christian minister to take his view, and to advocate the necessity of sinning, he is specially well-pleased. His personal attention to that parish is no longer required.
—edited and adapted from Half-Hours With St. Paul, Chapter 18.