I was recently reminded of a punishing passage from St Paul's First Epistle to the Corinthians that led me to write a quick apologetics article about it. The verse is 1 Corinthians 11:32,
But when we are judged by the Lord, we are disciplined so that we may not be condemned along with the world.
Paul is speaking of those Christians in Corinth who were abusing the Eucharist (1 Cor. 11:17-34) and as a result God was inflicting punishments on them, such as illnesses and even death (1 Cor. 11:29-30). What is noteworthy about verse 32 is that Paul says God is chastising these Christians precisely to get them to change their ways so that they will "not be condemned along with the world." This teaching poses a serious problem for Protestant theology, particularly Calvinism, because Justification by Faith Alone teaches that the Christian cannot ever be condemned because they say Jesus was already condemned in their place.
The only two objections I can foresee is for a Protestant to either argue (1) this condemnation somehow does not pertain to Justification, or (b) that this passage is not speaking of true Christians. But these are mere assertions and they do violence to the plain language of the text. For example, Paul uses terms like "judged" and "condemned," which would have to apply to the forensic categories of Justification. In fact, the phrase "condemned along with the world" can only refer to the damning to hell sentence that the unrepentant world will end up receiving. And if Paul is not talking about genuine Christians, then he cannot be using collective terms like "we" and speaking of chastisement, since chastisement pertains only to adopted children of God. So this verse solidly proves that not only are Christians not justified by faith alone, but that God chastises them when they turn to sin for a very grave reason: so that they will correct their ways and not end up getting damned in the end. (cf 1 Tim. 1:19-20; Rev. 3:19)