Learn then, and believe deeply that Divine Grace is offered and received in no other way than through the Divine Mysteries that are performed by the Apostles and their successors, as the Lord Himself ordained in the Church. And so that you may be more assured of this, I will bring to you some examples from the Holy Scriptures. Our Lord Himself, talking to Nicodemus, said: “You must be born from above” (Jn. 3:7), meaning spiritual rebirth by Divine Grace. But by what means would it come and operate? Did He say perhaps, “Believe, open your mouth, and Divine Grace will come into you and give you new birth?” Of course not. He did not say anything like that. What did He say? “Unless one is born of water and the Spirit, he cannot enter the kingdom of God” (Jn. 3:5). What else is this birth “by water and the Spirit,” other than holy baptism, the first Christian Mystery?
An incident that happened at Ephesus during a journey of the Apostle Paul verifies this point. When the Apostle came to Ephesus, he met twelve believers and asked them: “When you believed, did you receive the Holy Spirit?” And they answered, “We have heard nothing about the Holy Spirit.” “How then were you baptized?” the Apostle asked. “In John’s baptism,” they replied.
Then the Aposlte explained to them that the baptism of St. John the Forerunner was only a preparation for the faith in Christ. And after he completed the evangelical teaching to them, he baptized them with the Christain baptism. After the baptism, he laid his hands on them, and they received the Holy Spirit.
Do you see that baptism is one thing and the “laying on of hands” another? Divine Grace is given to the believer only through the “laying on of hands”. The Apostles later replaced this visible action with Chrismation and thus Chrismation was established as one of the Divine Mysteries of our Church.
These two incidents, with St. Nicodemus and with the faithful in Ephesus, are enough to assure you that Divine Grace is given through visible means, through the Divne Mysteries, and not through mental belief alone.
This is how Christ Himself established things. I will mention here the other Divine Mysteries:
The forgiveness of sins, into which one falls after baptism, is not done with simple, mental confession to God, but with confession that takes place before a spiritual father, in deep contrition and determination not to repeat the same sins.
The Mystery of Divine Eucharist creates a living union of the believer with our Lord Jesus Christ.
The power of Divine Grace for the continuation of the sanctifying work of the Church is delivered through the Mystery of ordination.
Two persons unite in one and create a blessed Christian family through the Mystery of Marriage.
The sick are cured through the Mystery of Holy Unction.
The Divine Mysteries are rivers of Divine Grace that provide life-giving water to the faithful. There is no other way, no other means for one to receive Divine Grace. Whoever proclaims another way is in error and deception! (Preaching Another Christ: An Orthodox View of Evangelicalism pp. 26-28)