The Fiftieth Day: PENTECOST
The name “Pentecost” comes from the Greek word meaning “fiftieth.” Like Easter, it is tied to a Jewish feast. 49 days (7 weeks, or “a week of weeks”) after the second day of Passover, the Jews celebrated the Feast of Weeks (Shavuot).
Passover celebrates the freeing of the Jews from slavery; Shavuot celebrates their becoming God’s holy people by the gift and acceptance of the Law; and the counting of the days to Shavuot symbolises their yearning for the Law.
From a strictly practical point of view, Shavuot was a very good time for the Holy Spirit to come down and inspire the Apostles to preach to all nations because, being a pilgrimage festival, it was an occasion when Jerusalem was filled with pilgrims from many countries.
Symbolically, the parallel with the Jews is exact. We are freed from the slavery of death and sin by Easter; with the Apostles, we spend some time as toddlers under the tutelage of the risen Jesus; and when he has left, the Spirit comes down on us and we become a Church. ~Universalis