On the afternoon or evening of Great and Holy Wednesday, the Sacrament or Mystery of Holy Unction is conducted in Orthodox parishes. The Sacrament of Holy Unction is offered for the healing of soul and body and for forgiveness of sins. At the conclusion of the service of the Sacrament, the body is anointed with oil, and the grace of God, which heals infirmities of soul and body, is called down upon each person. Orthodoxy does not view this Sacrament as available only to those who are near death. It is offered to all who are sick in body, mind, or spirit.
The express purpose of the Sacrament of Holy Unction is healing and forgiveness. Since it is not always the will of God that there should be physical healing, the prayer of Christ that God’s will be done always remains as the proper context of the Sacrament. In addition, it is the clear intention of the Sacrament that through the anointing of the sick body the sufferings of the person should be sanctified and united to the sufferings of Christ. In this way, the wounds of the flesh are consecrated, and strength is given that the suffering of the diseased person may not be unto the death of his soul, but for eternal salvation in the resurrection and life of the Kingdom of God. (Source: Greek Orthodox Archdiocese of America)