What role does the Holy Spirit play in our continuous sanctification and our steadfastness in the Holy God?

In baptism the Holy Spirit of God severed us from the wild and fruitless olive tree and grafted us into Christ Jesus the new olive tree (Rom. 11:17), and so transported us out of our barren life and into the holy life. But the work of the Holy Spirit does not stop at this point; He makes us steadfast in the Root (the Holy Son) so that the sap of the holy life can flow from the Root through the branches. And the branches do not remain the same as they are, but are always growing in the Root and bearing much fruit. This is the mystery of steadfastness, which in fact is the fullness of the gift of the Holy Spirit, who pledges our spiritual growth, pledges the growth of our new man in the sanctified life, that we may reach the measure of stature of the fullness of Christ.

The Lord Christ taught us that we need to be steadfast in Him through the Holy Spirit: “Abide in Me, and I in you. As the branch cannot bear fruit of itself, unless it abides in the vine, neither can you, unless you abide in Me. I am the vine; you are the branches. He who abides in Me, and I in him, bears much fruit; for without Me you can do nothing. If anyone does not abide in Me, he is cast out as a branch and is withered; and they gather them and throw them into the fire, and they are burned” (John 15:4–6).

And the apostles drew our attention to the work of God by which we are adopted in Him, in His Son Jesus Christ through the anointing of the Holy Spirit, by saying, “ Now He who establishes us with you in Christ and has anointed us is God, who also has sealed us and given us the Spirit in our hearts as a guarantee” (2 Cor. 1:21–22); “But the anointing which you have received from Him abides in you, and you do not need that anyone teach you … and just as it has taught you, you will abide in Him” (1 John 2:27); “And by this we know that He abides in us, by the Spirit whom He has given us” (1 John 3:24).

901 St. Ambrose of Milan, On the Holy Spirit 2.1.19 (NPNF II/10:117).

902 See Fr. Tadros Yacoub Malaty, The Holy Spirit Between the New Birth and Continuous Renewal (Arabic), second edition (2003): p. 9.

On this matter St. Ambrose says, “And then remember that you received the seal of the Spirit; the spirit of wisdom and understanding, the spirit of counsel and strength, the spirit of knowledge and godliness, and the spirit of holy fear (Isa. 11:2), and preserved what you received. God the Father sealed you, Christ the Lord strengthened you, and gave the earnest of the Spirit in your heart (2 Cor. 5:5), as you have learned in the lesson from the Apostle. The people cleansed [by baptism], rich with these adornments, hasten to the altar of Christ.”⁹⁰³