Memorial services in the Orthodox Churchby Fr Nicholas M. Elias
We know from the Bible that the souls of the departed in Christ, after they are freed from the body, live in another world, beyond this world. But where that world is, how the souls live in it, what language they speak, etc. we do not know, although we are so curious for such a knowledge.
However, it has not pleased God to reveal to us the secrets of the next world, and hence, His "holy men", the writers of the Bible (2 Pet. 1:21), would not write by their own imagination to satisfy human curiosity; therefore, their writings bear the seriousness of Gods inspiration, and thereby absolute trustworthiness.
The life of the souls in the other world is described in the Bible in parables and characters, the descriptions of which are accepted by our Church as standing for realities (Luke 16:22, Matt. 22:13, I Cor. 13:12, Heb 12:22, Rev. 2:10, 3:5, 21:8 etc). The souls of the departed, from their death to their Final Judgment, live in an intermediate state. In other words, if they had lived according to the will of God, their souls foretaste the Joys of Paradise; if they had deliberately set themselves against the will of God and their lives ended in sin and unrepentance, their souls foretaste the misery of Hell. Their Joy or punishment shall have its perfect realisation at the Last Judgement after the resurrection of the dead, when their nature will be restored to its integrity (John 5:29). In this intermediate state the disembodied souls retain a conscious existence. The term "sleep" used instead of death in the Orthodox Church, applies to the body rather than to the soul. We may rather expect a quickening of the spiritual powers of memory, thought and affection and an intensifying of their operations, when released from the burden of the flesh (Luke 16:22-25). The departed have not forgotten us, nor are they indifferent to us. Those who have pleased God with their holy life, the Saints, pray for us; the rest need our prayers; It is "a holy and wholesome thought to pray for the dead, that they might be delivered from sin" (11 Maccabees 12:45).
The prayers for the departed are as ancient as the Christian Church. Prayers for a merciful Judgment at the Last Day, have the sanction of the early Liturgies, of which the first is that of Saint James, the Lord's brother. Although we read in the Bible that there are sins for which "there is no forgiveness, either in this world or in the world to come" (Matt. 12:32), it is our brotherly duty and obligation to pray for the forgiveness of the departed. Our prayers can help those who repented even shortly before their death; not those who committed suicide (or Euthanasia) or those who of their own free will rejected the love of God and ignored His Justice to the end of their life. But as we do not know what is going on in one's mind, while living or dying, we must pray for the souls of all departed. So, our Church offers prayers for them at their funerals and burials and over their graves, but especially the Church offers the Bloodless Sacrifice for the repose of the departed.
For the same purpose we perform the Memorial Services (Mnimosyna) on the third, ninth and the fortieth day, as well as on the anniversary of one's death and on the Saturdays dedicated to the souls (Psychosavata), preparing boiled wheat (kolliva) for these Services. The kollyva represent the souls of the departed (John 12:24). At the end of the Liturgy, special hymns and prayers are offered over them for the repose of the departed. These memorial services cannot be replaced by donations or similar Pious acts. Our prayers for the souls of the departed are expressions of the brotherly unity of the living and the dead, aiming to influence the All-Merciful God to show mercy to them.
from The Divine Liturgy Explained