It is Pentecost Sunday. Many of you will have prayed Novenas to lead up to this great Solemnity to intercede for the purifying Holy Spirit to enter more deeply into each of your souls.
It is the Solemnity of Pentecost Sunday. It is one of the great and most ancient Feasts in our liturgical Calendar. It was celebrated early enough to the mentioned in the Acts of the Apostles and in St. Paul’s First Letter to the Corinthians. "It supplants the Jewish feast of Pentecost, which took place 50 days after the Passover and which celebrated the sealing of the Old Covenant on Mount Sinai."
It is called the Birthday of the Church because it is the moment when the apostles and the Blessed Virgin Mary receive the outpouring of the Holy Spirit while gathered in the Upper Room. The apostles are then enabled to “go out to the whole world and proclaim the Good News.” "Christ's mission is completed, and the New Covenant is inaugurated." 
At our Baptism, we received the grace of justification, enabling among other things to give us “the power to live and act under the prompting of the Holy Spirit through the gifts of the Holy Spirit.” When we received the Sacrament of Confirmation this brought us an increase of the Holy Spirit’s gifts. It gave us “a special strength of the Holy Spirit to spread the defend the faith by word and action as true witnesses of Christ, to confess the name of Christ boldly, and never to be ashamed of the Cross.”
It is Pentecost Sunday – a special day to invoke the Holy Spirit. St. Alphonsus Liguori (1696-1787), a Bishop and Doctor of the Church and founder of the Redemptorist Order composed the prayer below in which we too can ask the Holy Spirit to grant us anew His seven gifts.
PRAYER FOR THE GIFTS OF THE HOLY SPIRIT
I give You my heart and I offer my ardent thanksgiving for all the grace which You never cease to bestow on me.
O Giver of all supernatural gifts, who filled the soul of the Blessed Virgin Mary, Mother of God, with such immense favours, I beg You to visit me with Your grace and Your love and to grant me the gift of holy fear, so that it may act on me as a check to prevent me from falling back into my past sins, for which I beg pardon.
Grant me the gift of piety, so that I may serve You for the future with increased fervour, follow with more promptness Your holy inspirations, and observe your divine precepts with greater fidelity.
Grant me the gift of knowledge, so that I may know the things of God and, enlightened by Your holy teaching, may walk, without deviation, in the path of eternal salvation.
Grant me the gift of fortitude, so that I may overcome courageously all the assaults of the devil, and all the dangers of this world which threaten the salvation of my soul.
Grant me the gift of counsel, so that I may choose what is more conducive to my spiritual advancement and may discover the wiles and snares of the tempter.
Grant me the gift of understanding, so that I may apprehend the divine mysteries and by contemplation of heavenly things detach my thoughts and affections from the vain things of this miserable world.
Grant me the gift of wisdom, so that I may rightly direct all my actions, referring them to God as my last end; so that, having loved Him and served Him in this life, I may have the happiness of possessing Him eternally in the next. Amen.
 Acts. 20:16, https://www.thoughtco.com/pentecost-in-the-catholi...
 1 Cor. 16:18
 Mk. 16:15
 Catechism of the Catholic Church # 1266
 Ibid., # 1303
 Ibid., Cf. Council of Florence (1439): DS 1319; LG 11, 12.