Feast of Pentecost
The Theophany after the baptism of Jesus is regarded as a Revelation of the Most Holy Trinity. Mt. 3.16ff: He saw the Spirit of God descending as a dove and coming upon Him and behold a Voice from Heaven saying: This Is My Beloved Son in Whom I Am well pleased. The speaker is God the Father. Jesus is the Son of God, in fact the only one and therefore the true and proper Son of God; for the words beloved Son in Scriptural language means usually only son (cf., Gen. 22.2,12,16; Mk. 12.6). The Holy Ghost appears under a special symbol as an independent, personal Essence side by side with the Father and the Son.
In His solemn address at the Last Supper, Jesus promises another Helper (Paraclitus), the Holy Ghost or the Spirit of Truth, Whom He Himself AND the Father would send. Jn. 14.16: And I will ask the Father: and He shall send you another Paraclete that He may abide with you forever (cf., Jn. 14.26 and 15.26). The Holy Ghost Who Is sent, is clearly distinguished as a Person from the Father and the Son Who send Him. The apellation Paraclitus and the activities attributed to Him (teaching, giving witness) presuppose His personal subsistence.
In the Trinitarian formula of Christian Baptism - in which the mystery of the Most Holy Trinity is most clearly manifested - Mt. 28.19: Going therefore, teach ye all nations, baptizing them in the Name of the Father, and of the Son, and of the Holy Ghost, the unity of essence of the Three Persons is indicated by the singular form in the Name.
The Holy Ghost:
1) is a real Person. This is testified to by the Trinitarian formula of Baptism, the name Paraclitus = helper, representative which belongs to a person only (Jn. 14.16,26; 15.26; 16.7). Cf., 1 Jn. 2.1 in which Christ is called our Paraclitus (= representative, advocate with the Father), and by the fact that personal attributes are ascribed to the Holy Ghost; for example, the teaching of truth (Jn. 14.16; 16.13), the giving of testimony for Christ (Jn. 15.26), the knowledge of the mysteries of God (1 Cor. 2.10), the forecasting of future events (Jn. 16.13; Ac 21.11), the installation of episcopoi (the bishops), Ac 20.28.
2) is a Person distinct from the Father and the Son. This is attested by the Trinitarian formula of Baptism, the appearance of the Holy Ghost at the baptism of Jesus under a special symbol, and especially the parting discourses of Jesus, in which the Holy Ghost is distinguished, as one Who Is given or sent, from the Father and the Son Who send Him (Jn. 14.16,26; 15.26).
The Holy Ghost proceeds from the Father AND the Son. The Greeks, who denied this article of Faith and fell away from the Church through schism in A.D. 867 and A.D. 1053 fell under the Mohammedan yoke in the year 1453, and strangely enough on the feast of Pentecost.
3) is a Divine Person. The Name Holy Ghost and the Name God are used alternately. Ac 5.3ff: Ananias, why has Satan tempted thy heart that thou shouldst lie to the Holy Ghost? Thou hast not lied to men, but to God (1 Cor. 3.16; 6.19ff). In the Trinitarian formula of Baptism, the Holy Ghost is made equal to the Father and to the Son who are truly God. Again, Divine attributes are ascribed to the Holy Ghost. The Holy Ghost possesses the fullness of knowledge: He teaches all truth, presages future things, searches the innermost secrets of God (1 Cor. 2.10) and has inspired the Prophets of Old (2 Pet. 1.21; cf., Ac. 1.16).
"The Holy Ghost," says Tertullian, "is God of God, as light is of light." St. Cyril of Alexandria compares the Holy Ghost in His likeness to the Father and the Son, to the vapor arising from water, which is like in its nature to the water producing it. St. Isidore, commenting on these words of Christ: I drive out devils through the finger of God, says that as the finger is of the same nature as the body, so the Holy Ghost is of the nature of God. St. Athanasius writes that the Holy Ghost is called the finger of God, because it is only through Him that the Father and the Son enter into communication with men. Through Him it was that the tables of stone were written. In the second General Council of Constantinople in A.D. 381, it was defined that the Holy Ghost is eternal, omnipresent, omniscient, almighty in opposition to the heresy of Macedonius.
A most blessed Feast to all!