What is Baptism For The Dead?
1.
A doctrine promoted mostly (but not exclusively) by Mormon groups wherein a living believer is baptized for a dead person who was never baptized.
1 CORINTHIANS 15:22&29,
22) Just as in Adam all die, so also in Christ all will be made alive.
29) Otherwise, what will they do who practice BAPTISM FOR THE DEAD, if the dead are not to be raised? What then would be the point of being BAPTIZED FOR THE DEAD?
See