In 1 Corinthians 15:29, Paul asks:
Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead?
Baptism for the dead is an ordinance not practiced by any major religion in Joseph Smith’s day yet it was clearly practiced previously by the church and in ancient Judaism too.
John A. Tvedtnes commented:
Historical records are clear on the matter. Baptism for the dead was performed by the dominant church until forbidden by the sixth canon of the Council of Carthage in A.D. 397. Some of the smaller sects, however, continued the practice. Of the [Cerinthus] of the fourth century, Epiphanius wrote: “In this country—I mean Asia—and even in Galatia, their school flourished eminently and a traditional fact concerning them has reached us, that when any of them had died without baptism, they used to baptize others in their name, lest in the resurrection they should suffer punishment as unbaptized.” (Heresies, 8:7.)– John A. Tvedtnes -Proxy Baptism
Why did no other religion practice this ordinance if it was obviously part of the early church?