Baptism for the dead

only mentioned in 1 Cor. 15:29. This expression as used by the
apostle may be equivalent to saying, "He who goes through a
baptism of blood in order to join a glorified church which has
no existence [i.e., if the dead rise not] is a fool." Some also
regard the statement here as an allusion to the strange practice
which began, it is said, to prevail at Corinth, in which a
person was baptized in the stead of others who had died before
being baptized, to whom it was hoped some of the benefits of
that rite would be extended. This they think may have been one
of the erroneous customs which Paul went to Corinth to "set in
order."