The Orthodox conversion rites—Chrismation, Baptism, and the holy Eucharist—are a fulfillment of priestly types or shadows in the Old Testament.
Just as Israel was a nation of priests (Ex. 19:6), so too is the new covenant Church (1 Pet. 2:9). A description of priestly consecration can be read in Leviticus, mirroring the conversion rites for Orthodox Christians.
First, there is washing with water, along with a vesting of priestly garments:
And Moses brought forward Aaron and his sons and cleansed them with water. And he clothed him with a tunic and girded him with a sash and clothed him with an undergarment . . . And he placed upon him the oracular breastpiece and placed in the oracular breastpiece the symbol of clarity and the symbol of truth. And he placed the holy diadem upon his head and attached to the holy diadem, on the front of it, a thin plate of gold, consecrated and holy, in exactly the manner in which the Lord had charged Moses. —Leviticus 8:6–9 (Septuagint)
For laity, the connection between the old and new covenants is being washed in the waters of regeneration, and—as especially seen in the ancient Church or with infants today—the donning of baptismal garments. For clergy, such as deacons, priests, and bishops, the vesting of special tunics, sashes, breastplates, and even headgear is another inescapable fulfillment. While modern ‘scholars’ have asserted that vestments or other similar things were ‘pagan’ or ‘imperial’ additions, they actually go back to the Old Testament.
The ‘crown’ or diadem is connected in early Christianity with martyrdom (Rev. 2:10; 3:11). To receive Christian baptism is to receive one’s calling as a martyr for Christ. In the mystery of marriage, the man and woman wear crowns as a reminder of their self-sacrificial love for each other in Christ. All true love is self-sacrifice, and the Orthodox marriage service reminds us of this fact. Priests and bishops also wear mitres or kamilavka as a unique fulfillment of the crowns of Leviticus.
Together with these rites is an anointing with oil:
And Moses poured some of the oil for anointing upon the head of Aaron and anointed him and consecrated him. —Lev. 8:12
The mystery of chrismation is an obvious Christian fulfillment of this anointing. Olive oil is connected with the Holy Spirit, and this mystery is sometimes called in scripture the ‘laying on of hands’ (e.g. Acts 8:16–17). Being ‘Christians’ by name, we are those who have received the holy chrism. Christ means ‘anointed one,’ and as Christians—as those who have been anointed and united to God by the Holy Spirit—we are ‘of’ the anointed one. Besides consecration, oil is also used in the Church for healing, as with the mystery of holy unction (James 5:14).
The final part of a priestly consecration was animal sacrifice. Of that offering, the new priests cooked and ate a portion together with some bread (Lev. 8:31). For those joining the Church or being ordained to the priesthood, their first act is to receive the holy gifts. By partaking of the Eucharist, the new Christians or priests are fulfilling the final rite as priests set apart for God.
To convert to Orthodox Christianity is to be set apart as a priest of the new covenant. We are washed in the waters of baptism, adorned with new garments and the crowns of martyrs, anointed with sacred oil, and given the sacrifice of Christ in the holy and blessed Eucharist.
All of these ceremonies are summarized by the apostle Paul, not only as the climax of our own conversion, but also as a source of our assurance in Christ:
But you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus and by the Spirit of our God (1 Cor. 6:11) . . . [You are] those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit (Heb. 6:4).
In these words, the three essential parts of our conversion are reiterated: Baptism, Chrismation, and the Eucharist.
In all that we have seen above, ‘becoming a Christian’ is a calling to both martyrdom and the royal priesthood in Christ. It is not a guarantee of innumerable blessings, joy, or even personal fulfillment in this present life, but is rather a calling to come and suffer—to come and die—and to then be risen in our God who trampled death by death.