Pentecost (Greek: Πεντηκοστή [ἡμέρα], Pentēkostē [hēmera],” “the Fiftieth [day]”) is the Greek name for the Feast of Weeks, a prominent feast in the calendar of ancient Israel celebrating the giving of the Law on Sinai. This feast is still celebrated as Shavuot. Later, in the Christian liturgical year, it is also a feast commemorating the descent of the Holy Spirit upon the twelve Apostles of Christ.
Among Christians, Pentecost commemorates the descent of the Holy Spirit upon the Twelve apostles and other followers of Jesus as described in the Acts of the Apostles 2:1–31. For this reason, Pentecost is sometimes described by some Christians today as the “Birthday of the Church.
“And when the day of Pentecost was fully come, they were all with one accord in one place. And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Spirit, and began to speak with other languages, as the Spirit gave them utterance. And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven. Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language.”
While those on whom the Spirit had descended were speaking in many languages, the Apostle Peter stood up with theeleven and proclaimed to the crowd that this event was the fulfillment of the prophecy (“I will pour out my spirit”) In Acts 2:17, it reads: “‘And in the last days,’ God says, ‘I will pour out my spirit upon every sort of flesh, and your sons and your daughters will prophesy and your young men will see visions and your old men will dream dreams.” Acts 2:41 then reports: “Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.”
Peter stated that this event was the beginning of a continual outpouring that would be available to all believers from that point on, Jews and Gentiles alike. (Acts 2:39)