We ourselves boast in you among the churches of God concerning your endurance and faith in all your persecutions and the afflictions which you bear,
A plain indication of the righteous judgment of God, that you may be accounted worthy of the kingdom of God, for which also you suffer. (2 Thes. 1:4-5)

Establishing the souls of the disciples, exhorting them to continue in the faith and saying that through many tribulations we must enter into the kingdom of God. (Acts 14:22)

“The believers have been called into God’s kingdom and glory (1 Thes. 2:12). To enter into this kingdom, we need to pass through afflictions (Acts 14:22). Hence, the persecutions and afflictions are a plain indication of God’s righteous judgment, showing that we may be accounted worthy of the kingdom of God.”

(2 Thes. 1:5, footnote 2)