Commemoration is the prayerful remembrance of the names of the living and the deceased in the Orthodox Church during the Divine Liturgy, based upon faith in the power and efficacy of such commemoration before God, for the eternal good and salvation of those being commemorated. Coming to church for a service, the faithful submit commemoration lists to the priest in the altar, with the names of their living (on a list “For the health of”) and deceased (on a list “For the repose of) relatives. The priest reads these names during the proskomedia, taking out a wafer for each person being commemorated. Afterwards these wafers go into the Holy Chalice, and thus the names of all those commemorated are anointed by the Holy Blood of Christ after the consecration of the Holy Gifts.

The commemoration of the deceased has special significance in Christianity. Death and burial do not terminate the relations of Christian love that had bound the living with the deceased during the earthly life of the latter. The continuation of these relations is expressed and realized in the prayerful commemoration of the deceased. According to the teaching of the Gospel, God is not a God of the dead, but of the living, for all live unto Him (Luke 20:38). The Holy Scriptures confirm that the salvific power of prayer is boundless, if we ask according to the will of the Son of God (1 John 5:14-15). Christ died and arose, in order to have power over the dead and the living, and Himself descended into hell, in order to deliver the souls who were awaiting His coming with faith (1 Peter 3:19).

The prayerful commemoration of the deceased was regarded as a pious and godly act. The custom of commemorating the deceased became established in the Christian Church by the end of the 2nd and beginning of the 3rd centuries. Ever since communal church services were instituted, prayers for the deceased have become a permanent part of their structure. This is attested to by all ancient Liturgies, both those that were used or are being used in the Orthodox Church (the Liturgies of St. James the brother of the Lord, of St. Basil the Great, of St. John Chrysostome, and of St. Gregory Dialogos) and the liturgies of the Western Church (Roman, Spanish or Mozarabic, Gallican, and others), as well as the liturgies of other religious communities that had broken away from the Orthodox Church in ancient times, such as the Jacobites, Copts, Syrians, Nestorians, and Armenians. Apostolic acts speak of the commemoration of the deceased with great clarity, and in them we find prayers for the deceased during the serving of the Eucharist as a sacrifice for the living and the dead, as well as the mention of days on which it is especially suitable to commemorate the deceased. The Church Fathers and teachers of subsequent times, clarifying the meaning of the commemoration of the deceased and demonstrating its true image in prayers, the Eucharist, and charity, often affirm that the commemoration of the deceased is an apostolic institution and that it is observed by the entire Church. It triumphed over the fallacy of the Arians, who had denied the benefit of prayers for the dead. In the Western Churches the custom of commemorating the deceased was not in such widespread use as in the East. The days of commemoration that were strictly preserved in the East were little-known to the Latin Churches. Although the Western Church had preserved the custom itself of commemorating the deceased, it had nevertheless significantly weakened the true meaning and significance of commemoration by its teaching on the purgatory. While the Lutherans, having rejected the significance of the Eucharist as a sacrifice for the living and the dead, as well as prayerful entreaties to the saints and all association between members of the earthly and celestial Churches in general, naturally had to reject the relevance and significance of prayers for the deceased.

According to Orthodox teaching, the state of the spiritual entity of each deceased person is not determined completely before the Last Judgment and the universal resurrection of the dead. Each soul, irrespective of whether it initially ends up in paradise or hell, will take up its final place only after the end of the world and Christ's Last Judgment. Since until that moment the fate of the souls remains not completely determined, some of them, who had made some effort on earth for their salvation, may receive alleviation and even release from torments in the afterlife by God's boundless mercy and through the prayers of the Church, especially during the Liturgy (which explains the importance of submission of commemoration slips for the deceased by their relatives). According to Church tradition, there are many examples in the Lives of the Saints of the beneficial assistance of commemoration for those deceased in whose memory it is performed. Of special importance is the commemoration of the deceased immediately after their death and throughout the subsequent 40 days, since 40 days after their repose they are assigned a place in the other world until the universal resurrection of the dead. The daily prayerful commemoration of the deceased person during liturgies throughout this entire period is called the 40-day commemoration and is ordered by the newly-reposed person's family members.

In the Russian Orthodox Church, of special significance are the following established days of commemoration: Day of Rejoicing – the day of universal church commemoration of the deceased (the Tuesday of the second week after the feast of Christ's Resurrection), as well as the ancestral Saturdays. Ancestral Saturdays are as follows: the Saturday before the Sunday of the Last Judgment and before the feast of the Pentecost, as well as the second, third, and fourth Saturdays of the Great Lent. There is also the Saturday before the feast of St. Demetrius of Thessalonika (26 October/8 November), when all Christians, but especially all Orthodox warriors who had fallen on the field of battle, are prayerfully commemorated. This commemorative Saturday was initially established in memory of the Russian warriors who had fallen in the Battle of Kulikovo in 1380.