In this passage, Gregory discusses the nature of the miracle of Pentecost. The main concern is whether the Apostles spoke one language, and then the audience understood miraculously in their own, or they Apostles were themselves speaking many languages. He also discusses the tower of Babel, presenting Pentecost as a reversal. Likewise, he seems to touch briefly on the nature of spiritual gifts. Finally, he quotes a psalm, which he cites as evidence against an unnamed group of heretics “who divide the divine nature.” In translating, I’ve tried to be literal, but I have been idiomatic in places to improve the English. I’ve followed the Greek text of Sources Chretiennes volume 358. You may see the Greek at Charles Sullivan’s blog here. Several Latin translations, including Rufinus’ very early one, can be found here. As always, suggestions and corrections are welcome.
Gregory of Nazianzus. In Pentecostem. Oration 41.15-6.
 They were thus speaking in foreign languages, and not their own, and this was a great miracle: the message was being proclaimed by those who had not been instructed. This was sign to the unbelievers, not to the believers, so that it might be a sign of judgment against the unbelievers, for it is written, “’in different languages and in strange lips I will speak to this people, and thus they will not hear me,’ says the Lord.”
Then, “they were hearing.” But wait here for a bit, and let us raise the question about how to divide this sentence. The reading has an ambiguity, which arises because of punctuation. Were they each hearing their own language, which implies that once voice was resounding through the air, but that many were heard? Thus, as it was traveling through the air, so that I may speak more clearly, one language  became many.
Or, should we place a pause after “they were hearing,” and thus join “as they were speaking in their own languages” with what follows. Thus, those “who were speaking,” were speaking the languages of the audience, so that we might understand it as, “foreign languages.”  I much prefer this approach . In the former case, the miracle would belong more to the hearers than to the speakers. But in the latter, the miracle belongs to the speakers, who even as they were being accused of drunkenness were clearly working wonders by the Spirit through their voices.
 Certainly, though, the former division of languages is to be praised, that division which took place when these evil and atheistic men were building the tower and speaking the same language, just as some now dare to do. God, having ruined their shared knowledge by dividing their language, thus foiled their attempt. Because of this, the present miracle is all the more praiseworthy, for it flows from one spirit, is poured out to many, and unites us together once more. There is indeed a diversity of gifts, and this diversity requires another gift for the discernment of the better gift, since all of them have something worthy of praise. And this division is said to be good, about which David says, “Scatter, O Lord, and divide their languages!” Why? Because “they loved all the words of confusion, with a deceitful tongue.” Here, he most clearly accuses those tongues that divide the divine nature. But that is enough on this subject.
 See 1 Cor 14:20ff
 Several times in the passage, Gregory uses φωνή to mean language. This word generally means “sound” or “voice” but “language” is a possibility according to LSJ. Gregory is also likely pulling from Neoplatonic discussion of φωνή.
 There is some doubt about this phrase. Rufinus’ early Latin translation appears to be confused about Gregory’s preference on the matter, and it may be that his base text lacked this sentence. We have some fairly early Syriac translations (c. 700-800) that have the line (thanks to Charles Sullivan for untangling the Syriac).
 This passage is a bit opaque. As the French translation notes, διαφορά has two meanings: “diversity/difference” or “type.” Gregory uses both here. The talk about the “better” gift appears to allude to 1 Cor 12:31, where Paul instructs to “pursue the greater gifts.” According to Nicetas Heracleensis, Gregory is referring to the “complimentarity” of the gifts, whereby one gift, like “tongues” needs another gift “interpretation of tongues” to explain it. The gift of prophecy likewise requires the gift of discernment to understand properly.
 According to Nicetas Heracleensis, Gregory is referring to the Pneumatomachians (also known as the Macedonians), a semi-Arian group which denied the divinity of the Holy Spirit, and asserted that Jesus is of like substance (ὁμοιούσιος) rather than of the same substance (ὁμοούσιος) with the Father.