Pentecost

καὶ ἐπλήσθησαν πάντες πνεύματος ἁγίου, καὶ ἤρξαντο λαλεῖν ἑτέραις γλώσσαις καθὼς τὸ πνεῦμα ἐδίδου ἀποφθέγγεσθαι αὐτοῖς.

et repleti sunt omnes Spiritu Sancto et coeperunt loqui aliis linguis prout Spiritus Sanctus dabat eloqui illis.

All of them were filled with the Holy Spirit and began to speak in other languages as the Spirit gave them ability.

(Acts 2.4)

This is part of the Office of Readings for the Solemnity of Pentecost, taken from the treatise Against Heresies by St. Irenaeus:

The Spirit of wisdom and understanding, the Spirit of counsel and strength, the Spirit of knowledge and the fear of God came down upon the Lord, and the Lord in turn gave this Spirit to his Church, sending the Advocate from heaven into all the world into which, according to his own words, the devil too had been cast down like lightning.

If we are not to be scorched and made unfruitful, we need the dew of God. Since we have our accuser, we need an Advocate as well. And so the Lord in his pity for man, who had fallen into the hands of brigands, having himself bound up his wounds and left for his care two coins bearing the royal image, entrusted him to the Holy Spirit. Now, through the Spirit, the image and inscription of the Father and the Son have been given to us, and it is our duty to use the coin committed to our charge and make it yield a rich profit for the Lord.