Pentecost
What is Pentecost?
"The Spirit of the Lord fills the whole world, and holds all things together and knows every word spoken by man, Alleluia."
The Feast of Pentecost, celebrated the fiftieth day after Easter, commemorates the descent of the Holy Spirit on the Apostles and the birth of the Church. It is celebrated on the day of the ancient Jewish festival called the “Festival of Weeks,” also called Pentecost (and the source of the name of the Catholic feast). The Catholic feast of Pentecost has also been known as Whitsunday, from “White Sunday,” in reference to the white garments worn by those being baptized on the feast day.
Historically, this feast dates back to the first century and the days of the Apostles, but it appears that early on, being so closely bound to Easter, it was not observed as much more than the end of Paschaltide. The reference to Pentecost in Paul's first letter to the Corinthians likely refers to the older, established Jewish feast. The day as a celebration of the Holy Spirit coming down upon the Apostles was well established by the time of the Ecclesiastical writer Tertullian of the second and third century. However, for some time the duration varied; some fourth century writings describe Pentecost as lasting one week, though it was not kept with an octave, but only as a single day, in the west until a much later date.
– Adapted from the Catholic Encyclopedia
