“This is evidence of God’s righteous judgment, to make you worthy of the kingdom of God, for which in fact you are suffering.”
2 Thessalonians 1.5
“This” refers to the “persecutions and afflictions”, v. 4, that the Thessalonians were suffering. Suffering in this way is not evidence of God’s indifference or injustice. Rather, it is evidence of his righteousness and goodness.
Do not doubt God in whatever you are called upon to suffer. Show perseverance and faith in such moments. What is the goal God has in mind for you?