The Good News Translation translation of verse 16 leaves one slight difficulty unsolved. It carries into English an ambiguity of the Greek text, in which the pronoun “he” (of “he may encourage”) may refer to our Lord Jesus Christ, to God our Father, or to both acting jointly. Verse 17 is a continuation of the sentence begun in verse 16, so that the one who loved us and … gave us courage … is the same one who Paul desires may fill you with courage and strengthen you.
Fill you with courage is literally “encourage your hearts.” Any translation of “hearts” which suggest mere emotion is to be avoided (see 1 Thess. 2.4, where Good News Bible has “our motives”; cf. 1 Thess. 2.17, where Good News Bible has “our thoughts”). The Greek word for “heart,” like its Hebrew equivalent, sometimes means the whole “inner man,” as in 1 Peter 3.4. Good News Translation, along with Phillips Jerusalem Bible New English Bible Translator’s New Testament Bijbel in Gewone Taal Die Bibel im heutigen Deutsch Traduction œcuménique de la Bible, accordingly replaces “your hearts” by you. However, “heart” can also refer more precisely to judgment and will, as in Mark 7.21, cf. Jeremiah 5.21 (King James Version “without understanding,” Revised Standard Version “senseless”) and Job 12.4 (Revised Standard Version “understanding,” New English Bible “sense”). This would fit in excellently with Paul’s appeal to his readers in 2.1-3 to use good sense and judgment. Similarly, strengthen you is the opposite of being “shaken” (see notes on v. 2).
In a number of languages it is impossible to speak of “filling you (or “your hearts”) with courage,” but one may say “to cause you to be completely courageous,” “to cause you to have complete courage,” or “to cause you to stand up against any and all dangers.”
To always do and say what is good (literally “in every good deed and word”) correctly links always and good with both do and say. The implied meaning is not “strengthen you whenever you are doing or saying something good,” but “strengthen you so that you can do and say what is good” (or perhaps, as in vv. 9-10, “so that you can do and say all kinds of good things”). Good News Translation (cf. Barclay) brings this out. Knox‘s “confirm you in every right habit of action and speech” somewhat over-emphasizes the suggestion that the Thessalonians are already (at least in general, cf. chapter 3) doing and saying what is good. However, Paul by no means denies this.
It may be difficult in some languages to combine the concept of “strengthen” with the idea of doing and saying what is good. The basic underlying meaning of strengthen in this context is an increase in “capacity” or “ability.” In some instances one may wish to translate this as “make you continually able to always do and say what is good.” By the introduction of “continually” and “able,” the concept of abiding strength is clearly indicated.
Quoted with permission from Ellingworth, Paul and Nida, Eugene A. A Handbook on Paul’s Second Letter to the Thessalonians. (UBS Handbook Series). New York: UBS, 1976. For this and other handbooks for translators see here .