From Dom Guéranger's The Liturgical Year.

That we may thoroughly understand the meaning and influence of the season of the liturgical year upon which we have now entered, it is requisite for us to grasp the entire sequel of mysteries, which holy Church has celebrated in our presence and company; we have witnessed her services, and we have shared in them. The celebration of those mysteries was not an empty pageant, acted for the sake of being looked at. Each one of them brought with it a special grace, which produced in our souls the reality signified by the rites of the liturgy. At Christmas Christ was born within us; at Passiontide He passed on and into us His sufferings and atonements; at Easter He communicated to us His glorious, His untrammelled life; in His Ascension He drew us after Him, and this even to heaven’s summit; in a word, as the apostle expresses all this working, ‘Christ was formed in us.’[1]

But, in order to give solidity and permanence to the image of Christ formed within us, it was necessary that the Holy Ghost should come, that so He might increase our light, and enkindle a fire within us that should never be quenched. This divine Paraclete came down from heaven; He gave Himself to us; He wishes to take up His abode within us, and to take our life of regeneration entirely into His own hands. The liturgy of this Time after Pentecost signifies and expresses this regenerated life, which is to be spent on the model of Christ’s, and under the direction of His Spirit.

Two objects here offer themselves to our consideration: the Church and the Christian soul. As to holy Church, the bride of Christ, filled as she is with the Paraclete Spirit, who has poured Himself forth upon her, and from that time forward is her animating principle, she is advancing onwards in her militant career, and will do so till the second coming of her heavenly Spouse. She has within her the gifts of truth and holiness. Endowed with infallibility of faith and authority to govern, she feeds Christ’s flock, sometimes enjoying liberty and peace, sometimes going through persecutions and trials. Her divine Spouse abides with her, by His grace and the efficacy of His promises, even to the end of time; she is in possession of all the favours He has bestowed upon her; and the Holy Ghost dwells with her, and in her, for ever. All this is expressed by this present portion of the liturgical year. It is one wherein we shall not meet with any of those great events which prepared and consummated the divine work; but, on the other hand, it is a season when holy Church reaps the fruits of the holiness and doctrine, which those ineffable mysteries have already produced, and will continue to produce during the course of ages. It is during this same season that we shall meet with the preparation for, and in due time the fulfilment of, those final events which will transform our mother’s militant life on earth into the triumphant one in heaven. As far, then, as regards holy Church, this is the meaning of the portion of the cycle we are commencing.

As to the faithful soul, whose life is but a compendium of that of the Church, her progress, during the period which is opened to her after the pentecostal feasts, should be in keeping with that of our common mother. The soul should live and act in imitation of Jesus, who has united Himself with her by the mysteries she has gone through; she should be governed by the Holy Spirit, whom she has received. The sublime episodes peculiar to this second portion of the year will give her an increase of light and life. She will put unity into these rays, which, though scattered in various directions, emanate from one common centre; and, advancing from brightness to brightness,[2] she will aspire to being consummated in Him whom she now knows so well, and whom death will enable her to possess as her own. Should it not be the will of God, however, to take her as yet to Himself, she will begin a fresh year, and live over again those mysteries which she has already enjoyed in the early portion of previous liturgical cycles, after which she will find herself once more in the season that is under the direction of the Holy Ghost, till at last her God will summon her from this world, on the day and at the hour which He has appointed from all eternity.

Between the Church, then, and the soul, during the time intervening from the descent of the divine Paraclete to the consummation, there is this difference—that the Church goes through it but once, whereas the Christian soul repeats it each year. With this exception the analogy is perfect. It is our duty, therefore, to thank God for thus providing for our weakness by means of the sacred liturgy, whereby He successively renews within us those helps which enable us to attain the glorious end of our creation.

Holy Church has so arranged the order for reading the Books of Scripture during the present period as to express the work then accomplished, both in the Church herself and in the Christian soul. For the interval between Pentecost and the commencement of August, she gives us the four Books of Kings. They are a prophetic epitome of the Church’s history. They describe how the kingdom of Israel was founded by David, who is the type of Christ victorious over His enemies, and by Solomon, the king of peace, who builds a temple in honour of Jehovah. During the centuries comprised in the history given in those books, there is a perpetual struggle between good and evil. There are great and saintly kings, such as Asa, Ezechias, and Josias; there are wicked ones, like Manasses. A schism breaks out in Samaria; infidel nations league together against the city of God. The holy people, continually turning a deaf ear to the prophets, give themselves up to the worship of false gods, and to the vices of the heathen, till at length the justice of God destroys both temple and city of the faithless Jerusalem; it is an image of the destruction of this world, when faith shall be so rare, that the Son of Man, at His second coming, shall scarce find a vestige of it remaining.

During the month of August, we read the Sapiential Books, so called because they contain the teachings of divine Wisdom. This Wisdom is the Word of God, who is manifested unto men through the teachings of the Church, which, because of the assistance of the Holy Ghost permanently abiding within her, is infallible in the truth.

Supernatural truth produces holiness, which cannot exist, nor produce fruit, where truth is not. In order to express the union there is between these two, the Church reads to us, during the month of September, the books called ‘hagiographic’; these are Tobias, Judith, Esther, and Job, and they show Wisdom in action.

At the end of the world the Church will have to go through combats of unusual fierceness. To keep us on the watch, she reads to us, during the month of October, the Books of Machabees; for there we have described to us the noble-heartedness of those defenders of the Law of God, for which they gloriously died; it will be the same at the last days, when power will be ‘given to the beast to make war with the saints, and to overcome them.’[3]

The month of November gives us the reading of the Prophets: the judgments of God impending upon a world which He is compelled to punish by destruction are there announced to us. First of all, we have the terrible Ezechiel; then Daniel, who sees empire succeeding empire, till the end of all time; and finally the Minor Prophets, who for the most part foretell the divine chastisements, though the latest among them proclaim, at the same time, the near approach of the Son of God.

Such is the mystery of this portion of the liturgical cycle, which is called the Time after Pentecost. It includes also the use of green vestments, for that colour expresses the hope of the bride, who knows that she has been entrusted by her Spouse to the Holy Ghost, and that He will lead her safe to the end of her pilgimage. St. John says all this in those few words of his Apocalypse: ‘The Spirit and the bride say, Come!’[4]

[1] Gal. iv. 19.
[2] 2 Cor. iii. 18.
[3] Apoc. xiii. 7.
[4] Ibid, xxii. 17.