Not only in the Ambrosian codex is this fourth sermon on Pentecost, and the fifth which follows, but also in the Turin one, they are covered as homily 18 and 23 On Pentecost. How great, dearest brethren, is the care of the almighty God for the salvation of mortals, and with what affection of condescension, pitying human perils, He emptied the diabolical power, from this we can most fully and without doubt estimate: that He both drew us to the faith of the truth by the blood of His Son, and, by the granted visitation of the Holy Spirit, has strengthened the hearts of believers. For Christ redeemed us unto life, He raises us unto virtue, so that the grace which we received when the Son delivered it, we may preserve while the Spirit guards it.
We see indeed, beloved, that under the dispensation of the mystery the benefits of the Only-begotten of God and of the Holy Spirit are distinct, yet we perceive in both one and the same will and one sacrament of loving-kindness. For Christ is born of a woman for our salvation, but it is the Spirit who works together to fashion that very manhood in the Virgin, just as it was said to blessed Mary: 'The Holy Spirit shall come upon thee, and the power of the Most High shall overshadow thee' (Luke 1). The Son of God is likewise baptized for us in the Jordan, but to glorify His baptism the Holy Spirit is present from heaven in the form of a dove. And so far is their purpose one and their counsel one, that Christ promises the Spirit to men, and the Spirit proclaims Christ, as the Lord says:
'When the Comforter is come, whom I will send unto you from the Father, the Spirit of truth, who proceedeth from my Father, he shall testify of me' (John 15). Assuredly they proclaim one another by mutual testimonies, they who know that they reign in undivided majesty. In short, that we may know more clearly that they are parted by no division whatsoever, the Comforter Himself visits and enlightens those whom the Saviour has chosen as fit for His mysteries. For all mankind indeed the Lord Jesus hung upon the cross, but His Gospel would not have shone upon all, had not, by the gift of the Holy Spirit, when He granted the apostles the knowledge of diverse tongues, the Lord's passion come to the knowledge of all the nations.
For the Parthians and Medes, and the Elamites, and the other nations, as we have read, hear in their own tongues in Judea the mighty works of God and the remedies of life proclaimed. Who then, save the truly almighty God, could have accomplished this: that fierce minds might learn holy sanctity, and that barbarous speech might receive heavenly teaching? Let us therefore, brethren, venerate this Spirit with divine worship, in whom is the full power of regenerating and the authority of remitting sins, as the Lord instructs His disciples, saying: 'Go, teach all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit' (Matt. 28); and elsewhere: 'Receive the Holy Spirit:
whose sins you shall forgive, they are forgiven; and whose you shall retain, they are retained' (John 20). Who then is so mad as to doubt that He is God, to whom together with the Father and the Son belongs inseparable glory and an undivided name, who by common dominion both punishes the pride of the sinner and absolves the humility of him who confesses? From the beginning of the ages, dearest brethren, through the patriarchs and prophets, the Spirit himself promised us that the Son of God would come for the redemption of the world; for he foretold, many thousands of years beforehand, that He would be born of a Virgin, taking the flesh of the new man, that He would suffer injuries from the impious, reproaches and the cross, and likewise His resurrection from the dead.
When this was fulfilled through our Lord Jesus Christ, and the mystery perfected, He illumined the hearts of His apostles with the wondrous coming of His majesty, so that whereas before He had sung of His humility and passion, now, the devil being triumphed over and death conquered, He might proclaim the eternal glory of His kingdom. Yet this same Comforter our Redeemer Himself announced to His disciples would come from heaven not many days hence, and would be sent by the Father. And thus it comes to pass that, while the Spirit prophesies Christ the Only-begotten of God the Father, and while Christ promises the Spirit to come from the Father, and they proclaim one another beforehand by mutual attestation, they are believed to be one, to will one thing, and forever to be able to do one thing.
This, beloved, is the Holy Spirit who by the working of a more secret mystery enriched the Virgin's womb with heavenly fruitfulness. This is the Spirit who visited the baptism of Christ our Lord, seen indeed by John in the form of a dove, yet in silence, and did not deem His own voice necessary at that time, when the Father Himself spoke from heaven, saying: 'Thou art my beloved Son, in whom I am well pleased' (Matt. 3). And we are taught these things by the testimonies of the holy Scriptures for this reason, that there may be revealed to us a majesty indeed undivided in the persons, but a distinct property. For as far as pertains to the unity of the Godhead, in the Word of the Father the Spirit is consent, and in the utterance of the Spirit is the will of the Father.
For who, unless perhaps either an impious heretic or a faithless Jew, would doubt that the Holy Spirit is God, without whom neither is the sacrament of baptism perfected, nor the remission of sins granted? Who is so mad as to deny that He is God, blasphemy against whom is so impious and deadly that no pardon follows the sin of the blasphemer, as our Saviour declares, saying: 'He who shall speak a word against the Son of Man, it shall be forgiven him; but he who shall speak against the Holy Spirit, it shall not be forgiven him, neither in this world nor in the world to come' (Matt. 12). This Holy Spirit, I say, proceeding from the Father, promised by the Son, deigned to pour the gifts of His glory upon the apostles
which are Christ's, so that they might speak in the tongues of all nations of His passion and His kingdom. By this very condescension, since the whole human race was called to life, the whole world everywhere might hear the dispensation of the mysteries of God. How great a miracle it was, brethren, that a Hebrew man, suddenly bursting forth into words not his own, instructed the Greek concerning the mighty works of God, taught the Roman, addressed the Egyptian, and formed all the barbarous nations to the faith in their own tongues! And therefore, beloved, let us implore the mercies of almighty God, that we too may be able to announce concerning God the things that are worthy, and that you may be able to hear and understand with due reverence the things that are said, etc.