Another way of understanding baptism as our ordination service is to see that being clothed with Christ is a typological fulfilment of Aaron’s priestly garments (cf Exod. 28:2). Paul says this;
“You are all sons of God through faith in Christ Jesus, 27 for all of you who were baptised into Christ have clothed yourselves with Christ.” (Galatians 3:26)
Baptism, as believers, is baptism “into Christ”. And this passage in Galatians suggests that we are united with Christ as priests. For we have been clothed with Christ. If Jesus was the priest par excellence, and if we ‘wear’ Jesus Christ, or “put on the new self” then we wear the garment that qualifies us as NT priests.
In his book The Priesthood of the Plebs, Peter Leithart argues that Christian baptism fulfils and replaces Levitical ordination. I find this a most wonderful truth that will transform the way we think of ourselves as Christians. Let me quote a paragraph from his book that summarises why he makes such an important link:
“Like Christian baptism, the washing at the beginning of the ordination rite was an administered initiation, and in these respects the ordination bath was unique in the Levitical system. While most Old Testament ablutions were self-washings, Moses washed Aaron and his sons (Exod. 29:4; Lev. 8:6; cf. Lev. 14:8; 15:16-18, 27); while most cleansing rites were repeated as often as one became unclean, the ordination washing was once-for-all. Though priests washed their hands and feet before approaching the altar or approaching the tent (Exod.30:20), this self-washing was not a repetition of the ordination bath since it was partial and not administered. Similarly, when the Levites were set apart to help the priests in tabernacle service, Moses sprinkled them with water, then they shaved themselves and washed their clothes before being installed through a sacrificial rite and the laying on of hands (Num. 8:5-15). The ordination bath and the closely related sprinkling of the Levites were the only administered initiatory water “baptisms” in the Levitical system. [Italics his].” (The Priesthood of the Plebs, (Eugene, Wipf and Stock, 2003), p95)
Thus in baptism, Christians are ordained as priests into the New Testament Priesthood and our whole life is dedicated to the service and guardianship of Christ, the Gospel and the Temple (ie the Church).