In every thing give thanks: for this is the {f} will of God in Christ Jesus concerning you.

(f) An acceptable thing to God, and such as he approves well of.

People's New Testament

5:18 In every thing give thanks. Always be thankful for God's benefits, and always express your thanks. For scriptural examples, see Ac 27:35 2Co 1:11 Act 28:15 Eph 5:20.

This is the will of God. The three duties just named are probably comprehended (1Th 5:16,17).

Wesley's Notes

5:18 For this - That you should thus rejoice, pray, give thanks. Is the will of God - Always good, always pointing at our salvation.

Jamieson-Fausset-Brown Bible Commentary

18. In every thing-even what seems adverse: for nothing is really so (compare Ro 8:28; Eph 5:20). See Christ's example (Mt 15:36; 26:27; Lu 10:21; Joh 11:41).

this-That ye should "rejoice evermore, pray without ceasing, (and) in every thing give thanks," "is the will of God in Christ Jesus (as the Mediator and Revealer of that will, observed by those who are in Christ by faith, compare Php 3:14) concerning you." God's will is the believer's law. Lachmann rightly reads commas at the end of the three precepts (1Th 5:16-18), making "this" refer to all three.

Matthew Henry's Concise Commentary

5:16-22 We are to rejoice in creature-comforts, as if we rejoiced not, and must not expect to live many years, and rejoice in them all; but if we do rejoice in God, we may do that evermore. A truly religious life is a life of constant joy. And we should rejoice more, if we prayed more. Prayer will help forward all lawful business, and every good work. If we pray without ceasing, we shall not want matter for thanksgiving in every thing. We shall see cause to give thanks for sparing and preventing, for common and uncommon, past and present, temporal and spiritual mercies. Not only for prosperous and pleasing, but also for afflicting providences, for chastisements and corrections; for God designs all for our good, though we at present see not how they tend to it. Quench not the Spirit. Christians are said to be baptized with the Holy Ghost and with fire. He worketh as fire, by enlightening, enlivening, and purifying the souls of men. As fire is put out by taking away fuel, and as it is quenched by pouring water, or putting a great deal of earth upon it; so we must be careful not to quench the Holy Spirit, by indulging carnal lusts and affections, minding only earthly things. Believers often hinder their growth in grace, by not giving themselves up to the spiritual affections raised in their hearts by the Holy Spirit. By prophesyings, here understand the preaching of the word, the interpreting and applying the Scriptures. We must not despise preaching, though it is plain, and we are told no more than what we knew before. We must search the Scriptures. And proving all things must be to hold fast that which is good. We should abstain from sin, and whatever looks like sin, leads to it, and borders upon it. He who is not shy of the appearances of sin, who shuns not the occasions of it, and who avoids not the temptations and approaches to it, will not long keep from doing sin.