Why could Paul tell persecuted believers to rejoice always?

Paul could tell persecuted believers to rejoice always because the Thessalonian believers had the assurance that God was with them and that nobody could touch them without His knowing it. That settled confidence allowed Paul to rightfully write, "Rejoice evermore," even while they faced persecution and pressure.

Les explains that if you were under persecution and pressure, having somebody write "rejoice" might not seem to set right, yet Paul was so on target. These Thessalonian believers had this assurance that their God was with them, that nobody could touch them without His knowing it, and so Paul could rightfully write, "rejoice evermore." He then adds, "pray without ceasing," noting that when you are under persecution, that is pretty easy to do. By contrast, in America we have it so good most of the time that we think we have no need to get on our knees and spend 10, 15, 20 minutes a day in prayer, though God expects that of every believer and wants that communication.

1 Thessalonians 5:16

Rejoice evermore.

Why could Paul tell the suffering Thessalonian believers to rejoice evermore?

Paul could tell the suffering Thessalonian believers to rejoice evermore because they had assurance that their God was with them and that nobody could touch them without His knowing it. Even under persecution and pressure, that confidence remained, so Paul was on target and could rightfully write, “rejoice evermore.”