The clause may be literally translated, “at the revelation of the Lord Jesus.” The word used for “revelation” (apokalupsis) means “an unveiling,”“uncovering,” or “revealing” (see on 1 Cor. 1:7; Rev. 1:1). Paul identifies with the second advent of their Lord in glory the finding of rest by the believers. At that time recompense will be given to the righteous and the living wicked (see Additional Notes on Rev. 20, Note 2).
Rest.
Gr. anesis, “a loosening,”“relaxing,”“relief,” hence, “rest.” It should be noted that the word “rest” is here a noun, not a verb, as the KJV may seem to imply. Paul is contrasting the rewards of the persecutors and the persecuted. Persecutors will receive the tribulation they have meted out to others, whereas the persecuted will gain what they have longed for, that is, “rest.” The value of this “rest” is heightened by the knowledge that it will be enjoyed in company with the apostles. Converts and evangelists will triumph together. What an incentive to steadfastness this must have been to the persecuted Thessalonians!