I just finished listening to a pastor talking about Luke 7 – the story of Jesus raising the widows son. Farther along in his message, he related an experience about praying for his deceased wife, for the Lord to bless her, and used 2 Timothy 4:19 in conjunction with 2 Timothy 1:17,18 to say that Onesiphorus had died and that verse 18 was a prayer for him. Therefore, praying for the dead has precedent in the Bible. I don’t know exactly what the original language actually states – was Onesiphorus dead? Or is this just an extrapolation from the use of past tense words?
Praying for the dead is a Catholic tradition associated with their belief in purgatory. It’s to mitigate the punishment they believe the dead sometimes receive to purify them for heaven.
There’s disagreement among scholars as to whether Onesiphorus was alive or dead when Paul wrote 2 Timothy. But either way, you can’t use this passage to justify praying for the dead. Our guide for interpretation is always to find the clearest passage on a subject and use it to interpret those that aren’t as clear. For me the clearest one on the finality of death is Hebrews 9:27 which says man is destined to die once and after that to face judgment. To me this verse means that once a person dies, it’s too late to change their status through prayer.
Personally, I think Onesiphorus had likely passed away and Paul was voicing the customary hope among Jews that the dead would receive mercy at their time of judgment. These were not intercessory prayers, but rather expressions of condolence. We have a similar custom today. You’ll sometimes hear a person say, “May God rest his soul” upon learning of the death of a friend.