Leo XIII on Devotion to the Holy Ghost

Invoke the Holy Ghost
We ought to pray to and invoke the Holy Ghost, for each one of us greatly needs His protection and His help. The more a man is deficient in wisdom, weak in strength, borne down with trouble, prone to sin, so ought he the more to fly to Him who is the never-ceasing fount of light, strength, consolation, and holiness.

The Forgiveness of Sins
And chiefly that first requisite of man, the forgiveness of sins, must be sought for from Him: “It is the special character of the Holy Ghost that He is the Gift of the Father and the Son. Now the remission of all sins is given by the Holy Ghost as by the Gift of God” (Summ. Th. 3a, q. iii., a. 8, ad 3m). Concerning this Spirit the words of the Liturgy are very explicit: “For He is the remission of all sins” (Roman Missal, Tuesday after Pentecost).

Sweet Guest of the Soul
How He should be invoked is clearly taught by the Church, who addresses Him in humble supplication, calling upon Him by the sweetest of names: “Come, Father of the poor! Come, Giver of gifts! Come, Light of our hearts! O, best of Consolers, sweet Guest of the soul, our refreshment!” (Veni Sancte Spiritus). She earnestly implores Him to wash, heal, water our minds and hearts, and to give to us who trust in Him “the merit of virtue, the acquirement of salvation, and joy everlasting.” Nor can it be in any way doubted that He will listen to such prayer, since we read the words written by His own inspiration: “The Spirit Himself asketh for us with unspeakable groanings” (Rom 8., 26).

The Pledge of Our Inheritance
Lastly, we ought confidently and continually to beg of Him to illuminate us daily more and more with His light and inflame us with His charity: for, thus inspired with faith and love, we may press onward earnestly towards our eternal reward, since He “is the pledge of our inheritance” (Eph 1, 14). . . .

With the Blessed Virgin Mary
Unite, then, Venerable Brethren, your prayers with Ours, and at your exhortation let all Christian peoples add their prayers also, invoking the powerful and ever-acceptable intercession of the Blessed Virgin. You know well the intimate and wonderful relations existing between her and the Holy Ghost, so that she is justly called His Spouse. The intercession of the Blessed Virgin was of great avail both in the mystery of the Incarnation and in the coming of the Holy Ghost upon the Apostles. May she continue to strengthen our prayers with her suffrages, that, in the midst of all the stress and trouble of the nations, those divine prodigies may be happily revived by the Holy Ghost, which were foretold in the words of David: “Send forth Thy Spirit and they shall be created, and Thou shalt renew the face of the earth”( Psalm 103:30).

Pope Leo XIII
Encyclical, Divinum Illud Munus
9 May 1897