In the Church’s annual liturgical cycle, Pentecost is “the last and great day.” It is the celebration by the Church of the coming of the Holy Spirit as the end – the achievement and fulfillment – of the entire history of salvation. For the same reason, however, it is also the celebration of the beginning: it is the “birthday” of the Church as the presence among us of the Holy Spirit, of the new life in Christ, of grace, knowledge, adoption to God and holiness.

This double meaning and double joy is revealed to us, first of all, in the very name of the feast. Pentecost in Greek means fifty, and in the sacred biblical symbolism of numbers, the number fifty symbolizes both the fulness of time and that which is beyond time: the Kingdom of God itself. It symbolizes the fulness of time by its first component: 49, which is the fulness of seven (7 x 7): the number of time. And, it symbolizes that which is beyond time by its second component: 49 + 1, this one being the new day, the “day without evening” of God’s eternal Kingdom. With the descent of the Holy Spirit upon Christ’s disciples, the time of salvation, the Divine work of redemption has been completed, the fulness revealed, all gifts bestowed: it belongs to us now to “appropriate” these gifts, to be that which we have become in Christ: participants and citizens of His Kingdom.
 
Bron: ocafs.oca.org