Feast of the Espousals of the Blessed Virgin Mary and St. Joseph, January 23

It is certain that a real matrimony was contracted by Joseph and Mary. Still Mary is called "espoused" to Joseph ("his mother Mary was espoused to Joseph", Matthew 1:18) because the matrimony was never consummated. The term spouse is applied to married people until their marriage is consummated (Colvenerius, Cal. Marian., 23 Jan.).  (Source)

Excerpts below from Mystical City of God by Venerable Mary of Agreda: 

God spoke in sleep to the high priest, saint Simeon, and commanded him to arrange for the marriage of Mary, the daughter of Joachim and Anne of Nazareth; since He regarded Her with special care and love. The holy priest answered, asking what was his will in regard to the person, whom the maiden Mary was to marry and to whom She was to give Herself as Spouse. The Lord instructed Him to call together the other priests and learned persons and to tell them that this Maiden was left alone and an orphan and that She did not desire to be married; but that, as it was a custom for the firstborn maidens not to leave the temple without being provided for, it was proper She should be married to whomever it seemed good to them.

The most prudent Virgin, with a countenance betokening virginal modesty, answered the priest with great composure and humility: "Sir, as far as my inclinations are concerned, I desire to preserve perpetual chastity during all my life; for I wished to dedicate myself to God in the service of this holy temple in return for the great blessings which I have received in it; I never had the intention or the desire to enter the state of matrimony, since I consider myself incapable of fulfilling the duties connected with it. This was my inclination, but thou, my master, who art to me in place of God, wilt teach me what is according to his holy Will," "My Daughter," answered the priest, "thy holy desires are acceptable to the Lord; but remember, that no maiden of Israel abstains from marriage as long as we expect the coming of the Messias conformably to the divine prophecies. Therefore all who obtain issue of children among our people, esteem themselves happy and blessed. In the matrimonial state Thou canst serve God truly and in great perfection; and in order that Thou mayest obtain a companion according to the heart of God and who will be conformable to thy wishes, we will pray to the Lord, as I have told Thee, asking Him to single out a husband for Thee, who shall be pleasing to Him and of the line of David; do Thou also pray continually for the same favor, in order that the Most High may favor Thee and may direct us all."

This happened nine days before the one appointed for the execution and realization of their resolve. During this time the most holy Virgin multiplied her prayers, beseeching the Lord with incessant tears and sighs, to fulfill his divine pleasure in that which She had so much at heart. On one of those nine days the Lord appeared to Her and said to Her: "My Spouse and my Dove, let thy afflicted heart expand and let it not be disturbed or sad; I will attend to thy yearnings and to thy requests, I will direct all things, and will govern the priests by my enlightenment; I will give Thee a spouse selected by Myself, and one who will put no hindrance to thy holy desires, but who, by my grace will prosper Thee in them. I will find for Thee a perfect man conformable to my heart and I will choose him from the number of my servants; my power is infinite, and my protection and aid shall never fail Thee."

...On the day on which...our Princess Mary completed the fourteenth year of her life, the men, who at that time in the city of Jerusalem were descendants of the tribe of Juda and of the race of David, gathered together in the temple. The sovereign Lady was also of that lineage. Among the number was Joseph, a native of Nazareth. and then living in Jerusalem; for he was one of the descendants of the royal race of David. He was then thirty-three years of age, of handsome person and pleasing countenance, but also of incomparable modesty and gravity; above all he was most chaste in thought and conduct, and most saintly in all his inclinations. From his twelfth year he had made and kept the vow of chastity. He was related to the Virgin Mary in the third degree, and was known for the utmost purity of his life, holy and irreprehensible in the eyes of God and of men.

All these unmarried men gathered in the temple and prayed to the Lord conjointly with the priests. in order to be governed by the holy Spirit in what they were about to do. The Most High spoke to the heart of the highpriest, inspiring him to place into the hands of each one of the young men a dry stick, with the command that each ask his Majesty with a lively faith, to single out the one whom He had chosen as the spouse of Mary. And as the sweet odor of her virtue and nobility, the fame of her beauty, her possessions and her modesty, and her position as being the firstborn in her family was known to all of them, each one coveted the happiness of meriting Her as a spouse. Among them all only the humble and most upright Joseph thought himself unworthy of such a great blessing; and remembering the vow of chastity which he had made and resolving anew its perpetual observance, he resigned himself to God's will, leaving it all to his disposal and being filled at the same time with a veneration and esteem greater than that of any of the others for the most noble maiden Mary.

While they were thus engaged in prayer the staff which Joseph held was seen to blossom and at the same time a dove of purest white and resplendent with admirable light, was seen to descend and rest upon the head of the saint, while in the interior of his heart God spoke: "Joseph, my servant, Mary shall be thy Spouse; accept Her with attentive reverence, for She is acceptable in my eyes, just and most pure in soul and body, and thou shalt do all that She shall say to Thee." At this manifestation and token from heaven the priests declared saint Joseph as the spouse selected by God himself for the maiden Mary. Calling Her forth for her espousal, the Chosen one issued forth like the sun, more resplendent than the moon, and She entered into the presence of all with a countenance more beautiful than that of an angel, incomparable in the charm of her beauty, nobility and grace; and the priests espoused Her to the most chaste and holy of men, saint Joseph.

...She betook Herself with her spouse Joseph to Nazareth, the native city of this most fortunate married couple. Joseph, although he had been born in that place, had, by the providential disposition of circumstances, decided to live for some time in Jerusalem. Thus it happened that he so improved his fortune as to become the spouse of Her, whom God had chosen to be his own Mother.

...She spoke to her spouse Saint Joseph, and said to him:...At a tender age, being compelled thereto by the force of this truth, which, with the knowledge of the deceitfulness of visible things, his divine light made known to me, I consecrated myself to God by a perpetual vow of chastity in body and soul; his I am and Him I acknowledge as my Spouse and Lord, with fixed resolve to preserve for Him my chastity. I beseech thee, my master, to help me in fulfilling this vow, while in all other things I will be thy servant, willing to work for the comfort of thy life as long as mine shall last. Yield, my spouse, to this resolve and make a like resolve, in order that, offering ourselves as an acceptable sacrifice to our eternal God, He may receive us in the odor of sweetness and bestow on us the eternal goods for which we hope."

The most chaste spouse Joseph, full of interior joy at the words of his heavenly Spouse, answered Her: "My Mistress, in making known to me thy chaste and welcome sentiments, thou hast penetrated and dilated my heart. I have not opened my thoughts to Thee before knowing thy own. I also acknowledge myself under greater obligation to the Lord of creation than other men; for very early He has called me by his true enlightenment to love Him with an upright heart; and I desire Thee to know, Lady, that at the age of twelve years I also made a promise to serve the Most High in perpetual chastity. On this account I now gladly ratify this vow in order not to impede thy own; in the presence of his Majesty I promise to aid Thee, as far as in me lies, in serving Him and loving Him according to thy full desires. I will be, with the divine grace, thy most faithful servant and companion, and I pray Thee accept my chaste love and hold me as thy brother, without ever entertaining any other kind of love, outside the one which Thou owest to God and after God to me. In this conversation the Most High confirmed anew the virtue of chastity in the heart of saint Joseph, and the pure and holy love due to his most holy spouse Mary. This love the saint already had in an eminent degree, and the Lady herself augmented it sweetly, dilating his heart by her most prudent discourse.

By divine operation the two most holy and chaste Spouses felt an incomparable joy and consolation. The heavenly Princess, as one who is the Mistress of all virtues and who in all things pursued the highest perfection of all virtues, lovingly corresponded to the desires of saint Joseph. The Most High also gave to saint Joseph new purity and complete command over his natural inclinations, so that without hindrance or any trace of sensual desires, but with admirable and new grace, he might serve his spouse Mary, and in Her, execute his will and pleasure.

Blessed Virgin Mary Asks for Loving Devotion To St. Joseph

"My daughter, although thou hast described my spouse, Saint Joseph, as the most noble among the princes and saints of the heavenly Jerusalem; yet neither canst thou properly manifest his eminent sanctity, nor can any of the mortals know it fully before they arrive at the vision of the Divinity. Then all of them will be filled with wonder and praise as the Lord will make them capable of understanding this sacrament. On the last day, when all men shall be judged, the damned will bitterly bewail their sins, which prevented them from appreciating this powerful means of their salvation, and availing themselves, as they easily could have, of this intercessor to gain the friendship of the just Judge. The whole human race has much undervalued the privileges and prerogatives conceded to my blessed spouse and they know not what his intercession with God is able to do. I assure thee, my dearest, that he is one of the greatly favored personages in the divine presence and has immense power to stay the arms of divine vengeance.

"I desire that thou be very thankful to the divine condescension for vouchsafing thee so much light and knowledge regarding this mystery, and also for the favor which I am doing thee therein. From now on, during the rest of thy mortal life, see that thou advance in devotion and in hearty love toward my spouse, and that thou bless the Lord for thus having favored him with such high privileges and for having rejoiced me so much in the knowledge of all his excellences. In all thy necessities thou must avail thyself of his intercession. Thou shouldst induce many to venerate him and see that thy own religious distinguish themselves in their devotion. That which my spouse asks of the Lord in heaven is granted upon the earth and on his intercession depend many and extraordinary favors for men, if they do not make themselves unworthy of receiving them. All these privileges were to be a reward for the amiable perfection of this wonderful saint and for his great virtues; for divine clemency is favorably drawn forth by them and looks upon saint Joseph with generous liberality, ready to shower down its marvelous mercies upon all those who avail themselves of his intercession."

~ Blessed Virgin Mary to Venerable Mary of Agreda, excerpt from Mystical City of God ~

St. Joseph: Miracle of Holiness

I perceive a certain difference in the graces given to this great Patriarch and those vouchsafed to other saints; for many saints were endowed with graces and gifts that are intended not for the increase of their own sanctity, but for the advance of the service of the Most High in other souls; they were, so to say, gifts and graces freely given and not dependent upon the holiness of the receiver. But in our blessed Patriarch all the divine favors were productive of personal virtue perfection; for the mysterious purpose, toward which they tended and helped along, was closely connected with the holiness of his own life. The more angelic and holy he grew to be, so much the more worthy was he to be the spouse of most holy Mary, the depository and treasure-house of heavenly sacraments. He was to be a miracle of holiness, as he really was. This marvelous holiness commenced with the formation of his body in the womb of his Mother. In this the providence of God himself interfered, regulating the composition of the four radical humors of his body with extreme nicety of proportion and securing for him that evenly tempered disposition which made his body a blessed earth fit for the abode of an exquisite soul and well-balanced mind (Wisdom 8, 19). He was sanctified in the womb of his mother seven months after his conception, and the leaven of sin was destroyed in him for the whole course of life, never having felt any impure or disorderly movement. Although he did not receive the use of his reason together with this first sanctification, which consisted principally in justification from original sin, yet his mother at the time felt a wonderful joy of the Holy Ghost. Without understanding entirely the mystery she elicited great acts of virtue and believed that her Son, or whomever she bore in her womb, would be wonderful in the sight of God and men.

The holy child Joseph was born most beautiful and perfect of body and caused in his parents and in his relations an extraordinary delight, something like that caused by the birth of Saint John the Baptist, though the cause of it was more hidden. The Lord hastened the use of his reason, perfecting it in his third year, endowing it with infused science and augmenting his soul with new graces and virtues. From that time the child began to know God by faith, and also by natural reasoning and science, as the cause and Author of all things. He eagerly listened and understood profoundly all that was taught him in regard to God and his works. At this premature age he already practiced the highest kinds of prayer and contemplation and eagerly engaged in the exercise of the virtues proper to his youth ; so that, at the time when others come to the use of reason, at the age of seven years or more, Saint Joseph was a perfect man in the use of it and in holiness. He was of a kind disposition, loving, affable, sincere, showing inclinations not only holy but angelic, growing in virtue and perfection and advancing toward his espousal with most holy Mary by an altogether irreproachable life.

For the confirmation and increase of his good qualities was then added the intercession of the blessed Lady; for as soon as She was informed that the Lord wished Her to enter the married state with him, She earnestly besought the Lord to sanctify Saint Joseph and inspire him with most chaste thoughts and desires in conformity with her own. The Lord listened to her and permitted Her to see what great effects his right hand wrought in the mind and spirit of the patriarch Saint Joseph. They were so copious, that they cannot be described in human words. He infused into his soul the most perfect habits of all the virtues and gifts. He balanced anew all his faculties and filled him with grace, confirming it in an admirable manner. In the virtue and perfection of chastity the holy spouse was elevated higher than the seraphim; for the purity, which they possessed without body, Saint Joseph possessed in his earthly body and in mortal flesh; never did an image of the impurities of the animal and sensible nature engage, even for one moment, any of his faculties. This freedom from all such imaginations and his angelic simplicity fitted him for the companionship and presence of the most Pure among all creatures, and without this excellence he would not have been worthy of so great a dignity and rare excellence.

Also in the other virtues he was wonderfully distinguished, especially in charity; for he dwelt at the fountainhead of that living water, which flows on to eternal life (John 4, 14); he was in close proximity to that sphere of fire and was consumed without resistance. The best that can be said of the charity of our saint is what I have already said in the preceding chapter namely, that his love of God was really the cause of his mortal sickness and of his death. The manner of his death was a privilege of his singular love, for his sweet sighs of love surpassed and finally put an end to those of his sickness, being far more powerful. As the objects of his love, Christ and his Mother, were present with him always and as both of Them were more closely bound to him than to any of the woman-born, his most pure and faithful heart was unavoidably consumed by the loving effects of such a close union. Blessed be the Author of such great wonders and blessed be the most fortunate of mortals, Saint Joseph, who so worthily corresponded to their love. He deserves to be known and extolled by all the generations of men and all nations since the Lord has wrought such things with no other man and to none has He shown such love.

~ Venerable Mary of Agreda, from The Mystical City of God ~

Intercession of St. Joseph Is Most Powerful

"But I have been informed concerning certain other privileges conferred upon Saint Joseph by the Most High on account of his great holiness, which are especially important to those who ask his intercession in a proper manner. In virtue of these special privileges the intercession of Saint Joseph is most powerful:

first, for attaining the virtue of purity and overcoming the sensual inclinations of the flesh;

secondly, for procuring powerful help to escape sin and return to the friendship of God;

thirdly, for increasing the love and devotion to most holy Mary;

fourthly, for securing the grace of a happy death and protection against the demons in that hour;

fifthly, for inspiring the demons with terror at the mere mention of his name by his clients;

sixthly, for gaining health of body and assistance in all kinds of difficulties;

seventhly, for securing issue of children in families.

"These and many other favors God confers upon those who properly and with good disposition seek the intercession of the spouse of our Queen, Saint Joseph. I beseech all the faithful children of the Church to be very devout to him and they will experience these favors in reality, if they dispose themselves as they should in order to receive and merit them."

~ Venerable Mary of Agreda, from The Mystical City of God ~