1 Thess. 5:18. In everything give thanks:
The Apostle showed the path to constant joy, to unceasing prayer, and to thanksgiving. For whoever is accustomed to turning to God and thanks Him for everything that has served for his benefit — that person will obviously have constant joy.
For such is the will of God concerning you in Christ Jesus.
How then will you always give thanks? If you realize that it is the will of God for you to always be grateful to Him, as your constant benefactor in Christ Jesus, that is, through the cooperation of the Lord Jesus. For He Himself also cooperates with us in being thankful: He taught us to do that which we have learned from the Gospel.
1 Thess. 5:19. Do not quench the Spirit.
1 Thess. 5:20. Do not despise prophecies.
Since the present life is a night, God gave us a bright lamp — the Holy Spirit. But this lamp some made brighter, as all the saints did; while others extinguished it, as the five virgins who left it without oil, as the Corinthian fornicator who poured impurity into it. Therefore he said: "Do not quench the Spirit," that is, the gift. Lock the doors, that is, the senses, so that the spirit of wickedness does not enter and the lamp is not extinguished. Do not bring in earthly cares, and the lamp will remain unquenchable. Or it can also be understood this way: they had among them prophets of God and false prophets. Since it was unknown who was a true prophet, they turned away from all of them. Therefore the apostle says to them: "The Spirit," that is, the gift in the true prophets, "do not quench" by turning away as from false prophets, and do not despise prophecies from the Holy Spirit.
1 Thess. 5:21. Test all things, hold fast to what is good.
So then, what? Surely we should accept false prophets too? No, he says. But test all things, that is, examine both the false and the true with discernment, and then accept the prophecies that prove to be good, that is, regard them as true and keep them in mind.
1 Thess. 5:22. Abstain from every form of evil.
Not only from this or that, but simply from everything: both from false prophets and from sin.
1 Thess. 5:23. Now may the God of peace Himself sanctify you completely,
To his instruction the apostle also joins prayer, so that from both sides they might have security. What does "in all fullness" mean? That is, in body and soul, as is evident further on.
1 Thess. 5:23. and may your spirit and soul and body be preserved complete and blameless at the coming of our Lord Jesus Christ.
The Spirit, that is, the gift of the Holy Spirit, which we received through baptism. If we keep His lamp bright and unextinguished, then we shall enter the bridal chamber of the Bridegroom; and both soul and body will then be blameless, if the spirit within us shines brightly. Gregory of Nyssa says: since man is composed of every kind of soul — the physical soul, the sensory soul, and the rational soul — the apostle by the word "spirit" designated the rational part; by "soul" the sensory part; and by "body" the physical life within us. Thus, he prays that all of them and in all things be preserved blameless, in all things well-pleasing to God.
1 Thess. 5:24. Faithful is He Who calls you, Who will also do this.
Look, what humility! After he offered a prayer for them, he says: do not think that you will be saved by my prayers, but by the goodness of the God who called you. For if He called you to salvation, and He is faithful, that is, true, then He will certainly do according to His will and save you.
1 Thess. 5:25. Brethren, pray for us.
Pay attention to the humility: even Paul asked for their prayers.
1 Thess. 5:26. Greet all the brethren with a holy kiss.
Since he, being absent, could not greet them with a kiss from his own lips, he wishes to greet them through others, just as we also say: give so-and-so a kiss for me. And since there is also a treacherous kiss, like the kiss of Judas, he says: "with a holy kiss."
1 Thess. 5:27. I adjure you by the Lord to read this epistle to all the holy brethren.
Not so much for the sake of instruction, as for the sake of conversing with them through the epistle: a proof of ardent love. And he adjures them so that if they do not respect him, then at least for the sake of the oath they would fulfill what had been commanded to them. So fearful were adjurations for the early Christians! But alas, they are not such now, they are not such for us.
1 Thess. 5:28. The grace of our Lord Jesus Christ be with you. Amen.
All good things, he says, He has bestowed upon us. Therefore, strive to attract to yourselves the most abundant grace by living worthily of what has already been granted to you. And may this grace preserve us also from every unrighteous path; may we live to the glory of the Father and the Son and the Holy Spirit. To Him belongs all glory forever. Amen.