Jesus Christ taught that “except a man be born of water and of the Spirit, he cannot enter into the kingdom of God” (John 3:5). For those who have passed on without the ordinance of baptism, proxy baptism for the deceased is a free will offering. According to Church doctrine, a departed soul in the afterlife is completely free to accept or reject such a baptism — the offering is freely given and must be freely received. The ordinance does not force deceased persons to become members of The Church of Jesus Christ of Latter-day Saints or “Mormons,” nor does the Church list deceased persons as members of the Church. In short, there is no change in the religion or heritage of the recipient or of the recipient's descendants — the notion of coerced conversion is utterly contrary to Church doctrine.
Of course, proxy baptism for the deceased is nothing new. It was mentioned by Paul in the New Testament (see 1 Corinthians 15:29) and was practiced by groups of early Christians. As part of a restoration of New Testament Christianity, Latter-day Saints continue this practice. All Church members are instructed to submit names for proxy baptism only for their own deceased relatives as an offering of familial love. Baptisms for the dead are performed only in temples.
Montreal Quebec Temple