“This is a plain indication of God’s righteous judgment so that you will be considered worthy of the kingdom of God, for which indeed you are suffering” (2 Thessalonians 1:5).
The clearest indication of faith isn’t that you have joined a church, or been baptized. Those are things that Christians should do, but doing them doesn’t make or mean you are a Christian. Unfortunately, such things have given too many a false sense of security. Besides the fruit of the Spirit (Galatians 5), Paul writes that true faith is characterized by a continuing enlargement (v.3) and an indomitable spirit that endures to the end (v.4). Genuine faith does not breed indifference to the things of God, nor an apathy toward or an absence from the church.