Orthodox Christians Believe the physical body is a gift from God and that the body must now and always be treated with dignity and respect, and that the body does not belong to us; but is the essence of the Holy Spirit wherein the soul resides during our earthly journey.
Hence the Orthodox Church doctrine maintains that the body is equally as valuable on earth as is the soul in eternity. Eastern Orthodox tradition tells us that when we are resurrected upon the Second Coming of Christ, we will be resurrected in our physical bodies as was Jesus. Orthodox Christians believe that as Jesus was buried after being crucified (and not cremated as many were at that time) that they too are to be buried following the example of Jesus Christ.
The Orthodox Church does not allow for a funeral service to be conducted by an Orthodox Priest in an Orthodox Church for a person being cremated. There are (have been) exceptions where the Orthodox Christian met an unexpected tragic death wherein the deceased’s remains were compromised by acts or actions beyond ones control.
The existing practice of burial was consonant with the ancient traditions of the Church and thus the mode of burial which alone has been established and manifested as lawful is clearly evident from the funeral service. Therein it is plainly indicated that, after the conclusion of the funeral service, the body is committed to the earth: “And thus, taking up the remains, we go forth to the grave, all the people following, preceded by the priest. And the relics are placed in the grave. The hierarch, or priest, taking up dirt with a spade, spreads it above the relics in a cross-wise fashion, saying: ‘The earth is the Lord’s and the fulness thereof, the world and all that dwell therein. . .’ (Ps. 23:1). And thus, they cover the grave as usual.”
In regard to the burial of the bodies of departed Christians in the earth, the custom has indisputably been preserved in the Church without change from the first days of her existence, and therefore the Roman law, cited by Zonaras  and later by Bishop Nikodim in his interpretation of the 87th canon of St. Basil the Great, is applicable: “When there does not exist a written law, one ought to preserve the customs and usages”, and “one must keep the ancient customs as law.” The custom of burying the dead came to the New Testament Church from the time of the Old Testament and was preserved by Christians who lived among peoples that widely practiced cremation of their dead. Thus, the holy canons which guard all the customs of the Church command that the ancient custom of burying the dead in the earth be preserved.
The Greek Orthodox Church as recently as 2021 has stated that: “the burial of the dead human body in earth presupposes and implies faith in the Resurrection of the Dead at the Second Coming and signifies the hope and eschatological expectation of the life of the future century.
“The Church does not accept the incineration of the body for its members, for this is a temple of the Holy Spirit, an element of the image of the fallen man in the likeness of God and surrounds it with respect and honour as an expression of love to its anointed member and as a manifestation of faith in the resurrection shared by all. It is inconceivable for an Orthodox Christian to deny burial and opt for incineration.”
While there may be exceptions where the Christian Orthodox Church can accept cremated remains in the funeral service, firstly consult with the Funeral Directors at Orthodox Funerals who will guide you and provide you with accurate advice, with the blessings of the Orthodox Church Bishops and Priests.