1 Timothy 1:18-20
18 “This command I entrust to you, Timothy, my son, in accordance with the prophecies previously made concerning you, that by them you fight the good fight, 19 keeping faith and a good conscience, which some have rejected and suffered shipwreck in regard to their faith. 20 Among these are Hymenaeus and Alexander, whom I have handed over to Satan, so that they will be taught not to blaspheme.”
Prophecies previously made: Paul is likely referring to the Spirit’s revelation of Timothy’s ministry to the Gentiles. Paul is recalling this in order that Timothy may be reminded of his special calling in the midst of his battle against false doctrine.
Good conscience: Every human being has a conscience. But ultimately good works do not make our consciences right with God. Only the death and resurrection of Jesus make our conscience good before God. All who reject this reality suffer shipwreck in regard to their faith. In the context, Paul seems to be suggesting that Hymenaeus and Alexander were not true believers.