Did Saint Paul Pray for the dead?

With last Friday having been the Feast of All Soul’s Day, where the Church remembers those who are in Purgatory and in need of our prayers, I would be remiss not to highlight some of the Biblical basis for prayers for the dead:

May the Lord grant mercy to the family of Onesiphorus because he often gave me new heart and was not ashamed of my chains.
But when he came to Rome, he promptly searched for me and found me.
May the Lord grant him to find mercy from the Lord on that day. And you know very well the services he rendered in Ephesus. (2 Tim 1:16-18)

Given that Paul is speaking of Onesiphorus in the past tense, it seems probably that he’s dead. (It could be argued that perhaps he had apostasized, but since Paul says only good things about him, it doesn’t seem likely.) But in the final verse, we see Paul asking God to have mercy on Onesiphorus, implying that Paul thought prayers for the dead would have benefit for their souls. So, this is just one of the verses that imply prayer for the deceased is allowable and recommended.