By Metropolitan Hierotheos (Vlahos) of Nafpaktos
The descent of the Holy Spirit on the day of Pentecost does not indicate that It was previously absent from the earth and from people, but that, as we mentioned before, it operates in a different way. We can offer two points which interpret the descent of the Holy Spirit and Its different energy.
The first point is that on the day of Pentecost the Apostles understood that the Holy Spirit is a particular hypostasis and not a simple energy of God. The Holy Spirit, which appeared faintly in the Old Testament as a breath, as a sound, as the voice of a breeze, as an inspiration of the Prophets, is manifested at Pentecost “as a self-existing hypostasis”. Thus, when the events which manifested the hypostasis of the Son had been completed, there began the events which manifested the hypostasis of the Holy Spirit (St. Gregory Palamas).
The second point by which one can interpret the descent of the Holy Spirit on the day of Pentecost is that the Holy Spirit made the Disciples members of the Body of Christ and gave them the power to participate in Christ’s victory over death.
St. Nicodemos the Hagiorite, interpreting the descent of the Holy Spirit, uses passages from St. Nicetas Stethatos and St. Basil the Great, according to which it descended not like a servant, but like a master and with authority. Just as the Son and Word of God became incarnate of His own will, voluntarily, so also the Holy Spirit of Its own will made the Apostles members of the Body of Christ. Moreover, the will of the Father is also the will of the Son and the Holy Spirit, and vice versa. The energy and will of the Triune God are common to them.
Freedom is used differently for God, the angels and men. God is said to possess freedom “preeminently, supremely and supraessentially”. God cannot be compared with human data. The angels possess freedom naturally, but they exercise it without hindrance, they want to use it directly, because they have nothing to prevent them from acting on it, for they are not hindered by the body or any other opposing force. Human beings are independent and have freedom, but their free will has been traumatised and it is not easy for them to carry out their desires. This is why desire and free will need to be strengthened by God. In the Old Testament it says that he who listens “receives favour from the Lord” (Proverbs 8.35). And the Apostle Paul writes: “for it is God who works in you to will and to act according to his goog purpose” (Philippians 2.13).
This means that the Holy Spirit came down into the hearts of the Apostles and is working in men through their own will and not as servants. But men must respond to the energy of the Holy Spirit with their will, since God does not violate their freedom. However, desire and free will must be reinforced by God because in the fallen state man is enslaved, he is an attached being.
In general, when we speak of the descent of the Holy Spirit on the day of Pentecost, we cannot understand it as an incarnation, for only the Son and Word of God became incarnate, but as Its hypostatic manifestation in the world, which transformed the Disciples and changed them from mortal men to living members of the Body of Christ.
Metropolitan Hierotheos (Vlahos) of Nafpaktos, The Feasts of the Lord, 320-322