11 For such meditation and exercise in godliness, being at all times the habit of the saints, is urgent on us at the present time, when the divine word desires us to keep the feast with them if we are in this disposition. For what else is the feast, but the constant worship of God, and the recognition of godliness, and unceasing prayers from the whole heart with agreement? So Paul wishing us to be ever in this disposition, commands, saying, 'Rejoice evermore; pray without ceasing; in everything give thanks. ' Not therefore separately, but unitedly and collectively, let us all keep the feast together, as the prophet exhorts, saying, 'O come, let us rejoice in the Lord; let us make a joyful noise unto God our Saviour. ' Who then is so negligent, or who so disobedient to the divine voice, as not to leave everything, and run to the general and common assembly of the feast?
Which is not in one place only, for not one place alone keeps the feast; but 'into all the earth their song has gone forth, and to the ends of the world their words.' And the sacrifice is not offered in one place, but 'in every nation, incense and a pure sacrifice is offered unto God. ' So when in like manner from all in every place, praise and prayer shall ascend to the gracious and good Father, when the whole Catholic Church which is in every place, with gladness and rejoicing, celebrates together the same worship to God, when all men in common send up a song of praise and say, Amen; how blessed will it not be, my brethren!
Who will not, at that time, be engaged, praying rightly? For the walls of every adverse power, yea even of Jericho especially, falling down, and the gift of the Holy Spirit being then richly poured upon all men, every man perceiving the coming of the Spirit shall say, 'We are all filled in the morning with Your favour, and we rejoice and are made glad in our days. '
Source: Letters (New Advent)