Stained glass window of the fire of the Holy Spirit descending on Mary and the Apostles on Pentecost. At Saint Alphonsus Liguori Church, in Saint Louis, Missouri.
From the Jewish Encyclopedia:
Pentecost: Name given by the Greek-speaking Jews to the festival which occurred fifty days... after the offering of the barley sheaf during the Passover feast... It is called, too, the "closing season of the Passover"...Pentecost marks the closing of the Paschal season. The descent of the Holy Spirit as tongues of fire led to the Apostles preaching in all tongues, to all nations. It marks the birthday of the Catholic — that is, universal — Church, which is made up of all nations and not just God's chosen nation of Israel. With the gifts of the Holy Spirit, we have the Law written on our hearts, and not just on tablets of stone.
The traditional festival of Pentecost as the birthday of the Torah (= "the time our Law was given"), when Israel became a constitutional body and "a distinguished people," remained the sole celebration after the Exile...