An excerpt from Prof. A.I. Osipov's book "POSTHUMOUS LIFE. Deliberations of a contemporary theologian." Some people find him controversial because he doesn’t not claim the it’s only Christians who will be saved.
“There is no need to speak here about the elevated steps of sanctity - this is a separate and a big subject. The main thing is that the righteous (of both the Old Testament and the New Testament) are only those people, who have arrived at this cognition, to such a feeling of need in God-Saviour, but not those who simply believed (or believe) in His coming as in some historic event and are waiting for the earthy and celestial benefits from Him (by the way, not knowing what it is). Those who crucified Christ also believed in the coming of Messiah, but they believed as in some earthy event, which would bring them shalom, that is all the goods of the earth - by that they deeply distorted the image of Messiah and the very essence of their religion. "Even the demons believe and shudder" (James, 2, 19), but remain demons, and this can happen with a man too.
From here it becomes clear, why those who repented: a criminal, a tax collector, a whore - are the righteous in Christianity.
That is why let's not judge about the eternal lot of any single person: Orthodox, non-Orthodox, non-Christian and etc. - because we do not know either their spiritual state, or all objective circumstances of his life. We must know and judge about the truth and falsity, that means about the salvation or downfall of this or that belief, the way of moral and spiritual life offered by it, but we cannot and have no right to say about a single man (or a nation) that he has perished. Only the Church can proclaim such a judgment. And each Christian is destined to pray for the neigbour (Luke, 10, 29-37), live or departed, irrespective of his convictions. Thus the Spiritual council of St. Trinity Sergiev Lavra, expressing their censure in respect of the Catholic expansion on the territory of the modern Russia, and at the same time concluded: "We cannot undertake upon us the right to judge, whether Roman-Catholics be saved or not, or in what measure the grace is present in the Catholic Church. The judgment of this kind and knowledge belongs to God alone"[1].
The Christian belief gives the possibility for a man to get ready for the posthumous life: his fight against a sin, compulsion for the keeping up the Gospel commandments, repentance to clear oneself the way to God and to escape the after death sufferings.
"POSTHUMOUS LIFE":
www.aosipov.ru/texts/POSTHUMOUS.doc
Why do we pray for the dead?
Many people who call themselves Christians are offended when they hear that we pray for the dead. This begs the question: Why do we pray for the dead?
We do not find that dying is a proper reason to excommunicate people from the Church. Although they have died they are still the Body of Christ, and as such deserve our prayers and our love.
http://orthodox.net/redeemingthetime...y-do-we-do-it/
Here is a great article of the topic but it's in Russian. If someone is really interested, he or she may use Google Translate. In short, it was a practice of the ancient Church which was given to us by the Apostles. For example, the first Liturgy was written by the Apostle James, the Lord's brother. And his Liturgy included a prayer for departed saints. In the Book of Baruch, the prophet Baruch prays for deceased sons of Israel. The Books of the Maccabees (2 Maccabees) also includes prayer for the dead.
http://www.na-gore.ru/articles/luka_o_usopshih.htm
Prayer and the Departed Saints
By David C. Ford, Ph.D
http://www.protomartyr.org/prayer.html