It is highly unlikely that Joseph Smith would have known that the Early Church practiced this on his own.

[kirtland r.m.]

The following material was gleaned from fairlatterdaysaints.com. and it is a nice addition to the other many posts on the forum on this important topic.

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][2] 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.) [3]

"That baptism for the dead was indeed practiced in some orthodox Christian circles is indicated by the decisions of two late fourth-century councils. The fourth canon (fifth in some lists) of the Synod of Hippo, held in 393, declares 'the Eucharist shall not be given to dead bodies...nor baptism conferred upon them.' The ruling was confirmed four years later in the sixth canon of the Third Council of Carthage."[4]

"It also seemed good that the Eucharist should not be given to the bodies of the dead. For it is written: 'Take, Eat', but the bodies of the dead can neither 'take' nor 'eat'. Nor let the ignorance of the presbyters baptize those who are dead."[5]

No major religions in Joseph Smith's day believed in this doctrine. It is highly unlikely that Joseph Smith would have known that the Early Church practiced this. Even if he did read Corinthians and invented this belief from scratch, how did he come up with such a logical reason for its use? https://www.fairlatterdaysaints.org/evi ... r_The_Dead

[Niemand]

As I've said elsewhere, Mandaeans have practised baptism for the dead into the present day.