These garments are placed on the newly-baptized immediately after coming up out of he waters of baptism (the Orthodox baptize by immersion, even in the case of infant baptism). As the robe is being placed on the new Christian, the priest says the prayer: "The servant of God, N., is clothed with the robe of righteousness; in the Name of the Father, and of the Son, and of the Holy Spirit. Amen." and the choir sings: "Vouchsafe unto me the robe of light, O Thou who clothest Thyself with light as with a garment, Christ our God, plenteous in mercy."
In Orthodox theology the baptismal robe symbolizes the "Garments of Light" (i.e., the fullness of Divine grace) with which Adam and Eve were clothed in the Garden of Eden before the Fall of Man. Baptism is believed to cleanse the believer of all the sinful defilements both of original sin and personal sins and the white garment is symbolic of this. During the ektenia (litany) before baptism, the deacon prays "That he (she) may preserve this (her) baptismal garment and the earnest of the Spirit pure and undefiled unto the dead Day of Christ our God...", referring not so much to the material garment as to the spiritual cleansing it represents.
