Pentecost derives from the Greek term — Pentekoste — fiftieth day. The seven weeks, or fifty days counting inclusively, after the Hebrew Passover. The Christian churches have taken it over and regard it as commemorative of the descent of the Holy Ghost upon the apostles in tongues of fire, as recorded in the New Testament; and they have made it the seventh Sunday after Easter.

John 15:26-27,16:12-15

Jesus said to his disciples: ‘When the Advocate comes, whom I shall send to you from the Father, the Spirit of truth who issues from the Father, he will be my witness. And you too will be witnesses, because you have been with me from the outset.‘I still have many things to say to you but they would be too much for you now. But when the Spirit of truth comes he will lead you to the complete truth, since he will not be speaking as from himself but will say only what he has learnt; and he will tell you of the things to come. He will glorify me, since all he tells you will be taken from what is mine. Everything the Father has is mine; that is why I said: All he tells you will be taken from what is mine.’

- The coming of the Holy Spirit on the disciples, empowering them to preach.

The Great Commission

Jesus gives the Great Commission to His disciples to spread the Gospel.

commemorates the descent of the Holy Spirit upon the Apostles of Jesus while they were in Jerusalem celebrating the Feast of Weeks, as described in the Acts of the Apostles (Acts 2:1–31).[2] The Catholic Church believes the Holy Spirit descended upon Mary, the mother of Jesus, at the same time, as recorded in the Acts of the Apostles (Acts 1:14).

Since its date depends on the date of Easter, Pentecost is a "moveable feast".

The Tongues of Fire at Pentecost

‎"When the day of Pentecost came, they were all together in one place. ‎Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. ‎They saw what seemed to be tongues of fire that separated and came to rest on each of them. ‎All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them." ‎— ‎Acts 2:1–4 (NIV)

‎ ‎ The same “secret fire” of the alchemist

Helena Blavatsky compared Pentecostal fire to the “descending flame” of divine wisdom that awakens latent faculties in humanity. The tongues of fire upon the head correspond, in occult anatomy, to the crown chakra ignited by the rising Kundalini. ‎ Meister Eckhart wrote that the soul must be “set ablaze by the living fire of God” in order to know divine truth.

Jacob Boehme described fire as the primal quality in which light and love are revealed. For him, Pentecost was the moment when the inner spark of divinity in humanity was fully kindled, making the apostles “flames that bore God’s word into the world.”

‎ ‎The rabbis taught that when the Torah was given at Sinai, it came as “flames of fire, divided, and every people heard it in their own language.” ‎

Cornelius Agrippa, in his Three Books of Occult Philosophy, spoke of the fiery spirit as the source of all magical utterance: words charged with spirit become forces that alter reality.

Rudolf Steiner described Pentecost as the “universalization of the Logos”...a moment when the Word became accessible to all peoples, each tongue carrying the creative fire.

Fire as the medium of divine communication: Agni in the Vedas as messenger between gods and men, Hestia’s eternal flame in Greece, the sacred fire of Zoroastrian temples.