A frequently asked question. Here’s an interesting explanation by Father David Dwyer of Busted Halo Ministeries:
The practice of praying for the dead is rooted first in Christian belief in the everlasting life promised in Jesus’ teachings and foreshadowed by his disciple’s experience that God had raised him from the dead. After death, even though separated from our earthly body, we yet continue a personal existence. It is as living persons that God invites us into a relationship whose life transcends death.
Praying for the dead has further origins in our belief in the communion of saints. Members of this community who are living often assist each other in faith by prayers and other forms of spiritual support. Christians who have died continue to be members of the communion of saints. We believe that we can assist them by our prayers, and they can assist us by theirs.
Our prayers for the dead begin at the moment of death. Often family members will gather in prayer around the bedside of the person who has died. The Order of Christian Funerals includes a Vigil Service for the deceased, which can be held in the home, in the church, or in a funeral home chapel, the funeral Mass and the Rite of Committal (which generally takes place at the burial site).
The prayers express hope that God will free the person who has died from any burden of sin and prepare a place for him or her in heaven. Death remains a mystery for us–a great unknown. Yet Christian language evokes a hopeful imagination in the presence of death, an assurance that our love, linked to Christ’s love, can help bridge whatever barriers might keep those whom we love from fully enjoying the presence of a loving and life-giving God.