1 Corinthians 15:29

reads:

“Otherwise what will they do, those who are baptized for the dead, if the dead do not rise at all?  Why are they then baptized for the dead?”

Now, this verse has caused a lot of controversy, and a few groups have gone so far as to, on the basis  of it, institute practices in which living people are baptized on behalf of the dead.

But with a verse like this, where the strange phrase which simply mentions ‘baptism of the dead’ without elaboration, it seems a bit rash to start a whole new practice based on it.  Perhaps a more likely explanation is what the NET Bible notes suggest:

some Corinthians had undergone baptism to bear witness to the faith of fellow believers who had died without experiencing [it]. . . . Paul’s reference . . .  is neither a recommendation nor a condemnation. He simply uses it as evidence . . .  to bolster his larger argument, begun in 15:12, that resurrection from the dead is a present reality in Christ and a future reality for them.

That would make sense.  And so, if the NET translators are right, the point of the passage is the reality of the resurrection, and whether the early Corinthians did or did not practice some sort of baptism for the dead at some point is a question of historical and not doctrinal significance, as nowhere in the Bible do we any encounter any hint of a recommendation for any sort of baptism for the dead.