It is known to you all, brethren, how great is the venerable solemnity of this day, and with what joys so great a festival is to be celebrated by all. For today has been fulfilled that promise of our Saviour, by which He had said that He would send the Holy Spirit upon the apostles when He Himself should ascend into heaven. For He had promised: 'But when I have ascended to the Father, I will send you the Comforter, the Spirit of truth, and He shall teach you all things' (John 16). For we believe that the Son has truly reached the Father, when we see that the Comforter has descended upon the holy apostles. Him indeed we do not doubt to be reigning in heaven, when we see Him bestow the most sacred gifts of the Holy Spirit upon the earth.
Surely the Victor now sits at the right hand of the Father, while as Victor He lavishes gifts. Whence also the Saviour, the Victor over the devil, after His triumph enriched the disciples, whom He had freed from that one's captivity, also with the blessing of the Holy Spirit. He freed us when, for our rising again, He closed hell against us through Himself; He enriched us when, for our reigning, He unlocked heavenly things to us through the Comforter. For then we learned to return from death to life; but now we are taught to ascend from the earth to the heavens, as it is written: 'He shall teach you all things' (John 16). But what does that Holy Spirit teach? Assuredly He knows only to teach that which is holy. What does the Comforter intimate to us? That, assuredly, which the Saviour says:
'I have yet many things to say unto you, but ye cannot bear them now. When that Spirit of truth is come, He shall teach you all things' (John 16). A good teacher therefore is the Comforter, because He teaches the things which Christ reserved to be said. For the Holy Spirit teaches that which the Lord says He has to be taught. Plainly He is the best teacher, who is the executor of the Saviour's precepts. It is necessary, therefore, that His nature be of one substance with Christ, whom we see to be of one teaching with Christ. And therefore, beloved, let us cleanse ourselves from every defilement of the flesh, that we too may be worthy to receive the Holy Spirit.
If now we forsake the world with its pleasures and lusts, we too, like the apostles, shall have the Comforter, the Spirit of truth indeed, whom the Father will send us, since there is no respect of persons with God: therefore if we shall study to fulfill the law of the Lord, which is spotless and converts souls; if we shall study to perform the commandments sweeter than honey and the honeycomb, we shall attain to that eternal fatherland which God Himself has prepared for us; which may He Himself deign to grant. Here it ends.