In the sixth chapter of the first book of On the Holy Spirit by St. Ambrose, there is an interesting witness to the rite of baptism:
There are, however, many who, because we are baptized with water and the Spirit, think that there is no difference in the offices of water and the Spirit, and therefore think that they do not differ in nature. Nor do they observe that we are buried in the element of water that we may rise again renewed by the Spirit. For in the water is the representation of death, in the Spirit is the pledge of life, that the body of sin may die through the water, which encloses the body as it were in a kind of tomb, that we, by the power of the Spirit, may be renewed from the death of sin, being born again in God.
There are three things I’d like to highlight about this passage:
Firstly, though he doesn’t quote it, St. Ambrose does a marvelous job of explaining St. Paul’s claim in Galatians 2:20:
I have been crucified with Christ; it is no longer I who live, but Christ lives in me.
In baptism, our fallen selves are crucified and buried in the tomb of water. When we are sealed with the gift of the Holy Spirit, we are united to the humanity that sits at the right hand of the Father in perfect communion with the Holy Spirit — Christ. Through the baptismal rite we have been created anew in the image of Christ Himself, no longer of the world but of the Kingdom of Heaven.
Secondly, St. Ambrose implies that baptism by water and baptism by the Spirit are two separate actions within the baptismal rite. This is confirmed a few paragraphs later:
Do we live in the water or in the Spirit? Are we sealed in the water or in the Spirit? For in Him we live and He Himself is the earnest of our inheritance, as the Apostle says, writing to the Ephesians: ‘In Whom believing ye were sealed with the Holy Spirit of promise, Who is an earnest of our inheritance’ (Eph. 1:13,14). So we were sealed by the Holy Spirit, not by nature, but by God, for it is written: ‘He Who anointed us is God, Who also sealed us, and gave the earnest of the Spirit in our hearts’ (2 Cor. 1:21) . . . For although we were visibly sealed in our bodies, we are in truth sealed in our hearts, that the Holy Spirit may portray in us the likeness of the heavenly image.
This appears to be a witness to the Orthodox practice of chrismation — when Orthodox Christians are anointed with myrrh and sealed with the gift of the Holy Spirit Himself at their baptism. In Western Christendom, this practice was separated from the baptismal rite and became known as confirmation, and in process, lost its original liturgical significance.
Finally, note how this act of chrismation — sealing — is ontological in nature (ontology means the study of being — from the Greek ὄντος meaning that which is and-λογία meaning study). This isn’t a life-style choice or something limited to reason and rational thought. It is a radical change in our very being. Once sealed with the gift of the Holy Spirit, we are no longer beings of the fallen world — we are the children of God who bring with them the Kingdom of Heaven, in the presence of the Holy Spirit, everywhere we go. Amen.