"And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ" (1 Thessalonians 5:23).
The words "I pray God" are in italics in the Authorised Version indicating that they are not to be found in the original Greek text, although this is along the lines of what Paul is saying. Young, in his Literal translation uses the word "may" for this phrase, as does the Diaglott.
The word 'And' which starts this verse is linking the content with that which comes before; Paul is not saying that God would sanctify them regardless of their way of life, but because of their adherence and obediance to the principles of failthful discipleship through which they are "children of light" and "appointed... to obtain salvation by our Lord Jesus Christ" (1 Thessalonians 5:5-91 Thessalonians 5:5-9 5 Ye are all the children of light, and the children of the day: we are not of the night, nor of darkness. 6 Therefore let us not sleep, as do others; but let us watch and be sober. 7 For they that sleep sleep in the night; and they that be drunken are drunken in the night. 8 But let us, who are of the day, be sober, putting on the breastplate of faith and love; and for an helmet, the hope of salvation. 9 For God hath not appointed us to wrath, but to obtain salvation by our Lord Jesus Christ,). And so Paul is here indicating his wishes are that Yahweh would make or declare the saints at Thessalonica separate from the world and dedicated to their faith, as the Greek word translated "sanctify" can mean both of these things. The outcome of this sanctification would be the preservation of their whole spirit (character), soul (life) and body as he goes on to explain. All of these three are attributes that will be reinstated at the resurrection and will go on to be preserved in those that are judged worthy of eternal life but in a body energised by the Divine nature. Those judged unworthy of eternal life will ultimately lose all three in death.
In addition Paul is not only hoping that the disciples would be wholly sanctified but that they would be blameless until the coming of the Lord Jesus Christ from heaven. Therefore, this indicates their whole and complete separation from the things of the world, and their dedication to their God so that they bore the "fruits of the spirit", would mean that they were without censure in the eyes of Yahweh. We obviously need to maintain the same, being in the world, but not of the world and separate from it and all of its ungodly ideas and practices (Jude 12-18Jude 12-1812 These are spots in your feasts of charity, when they feast with you, feeding themselves without fear: clouds they are without water, carried about of winds; trees whose fruit withereth, without fruit, twice dead, plucked up by the roots; 13 Raging waves of the sea, foaming out their own shame; wandering stars, to whom is reserved the blackness of darkness for ever. 14 And Enoch also, the seventh from Adam, prophesied of these, saying, Behold, the Lord cometh with ten thousands of his saints, 15 To execute judgment upon all, and to convince all that are ungodly among them of all their ungodly deeds which they have ungodly committed, and of all their hard speeches which ungodly sinners have spoken against him. 16 These are murmurers, complainers, walking after their own lusts; and their mouth speaketh great swelling words, having men’s persons in admiration because of advantage. 17 But, beloved, remember ye the words which were spoken before of the apostles of our Lord Jesus Christ; 18 How that they told you there should be mockers in the last time, who should walk after their own ungodly lusts. ) ensuring that such are permitted within the ecclesia, the household of God.