http://www.fairlds.org/apol/misc/misc23.html, is a Mormon web site defending their practice of baptism for the dead. I know our church does not practice baptism for the dead now, but did it ever?
Baptism for the dead is a false practice never observed by the Church. This practice is useless since after death there is not repentance.
In 1 Corinthians 15:29 St Paul shows the absurdity of this false belief by saying "Else what shall they do who are baptized for the dead, if the dead rise not at all? Why are they then baptized for the dead?" Some of the Corinthians, influenced by their pagan upbringing, were still practicing baptism for the dead. At the same time they doubted the resurrection from the dead. What then is the use of Baptism for the dead who still remain dead?
There is no historical or traditional evidence to the claim of this article that our Coptic Church ever practiced this false practice.
This article already states the rarity of this practice "That the practice was considered rare and even aberrant by the fourth century is evidenced by the fact that only the Marcionites of that era are said to have continued such baptisms". It is clear that this practice was limited to a certain category of people who were a heretical sect founded in A.D. 144 by Marcion in Rome. They rejected the writings of the Old Testament and taught that Christ was not the Son of the God of the Jews, but the Son of the good God, who was different from the God of the Ancient Covenant. The article mentions several early fathers' writings against the Marcionites. St. John Chrysostom in his comment on baptism for the dead writes:
'What then is that which he means? Or will ye that I should first mention how they who are infected with the Marcionite heresy pervert this expression? And I know indeed that I shall excite much laughter; nevertheless, even on this account most of all I will mention it that you may the more completely avoid this disease: viz., when any catechumen departs among them, having concealed the living man under the couch of the dead, they approach the corpse and talk with him, and ask him if he wishes to receive baptism; then when he makes no answer, he that is concealed underneath saith in his stead that of course he should wish to be baptized; and so they baptize him instead of the departed, like men jesting upon the stage. So great power hath the devil over the souls of careless sinners. Then being called to account, they allege this expression, saying that even the Apostle hath said, "They who are baptized for the dead. Seest thou their extreme ridiculousness?" (St John Chrysostom, Homily XL, on 1 Corinthians).