They began to speak He showeth that the effect did appear presently, and also to what use their tongues were to be framed and applied, But because Luke setteth down shortly after, that strangers out of divers countries did marvel, because that every one of them did hear the apostles speaking in their own tongue, some think that they spoke not in divers tongues, but that they did all understand that which was spoken in one tongue, as well as if they should hear their natural tongue. [1] Therefore, they think that one and the same sound of the voice was diversely distributed amongst the hearers. Another conjecture they have, because Peter made one sermon in the audience of many gathered together out of divers countries, who could not understand his speech (and language,) unless another voice should come unto their ears than that which proceeded out of his mouth. But we must first note that the disciples spoke indeed with strange tongues; otherwise the miracle had not been wrought in them, but in the hearers. So that the similitude should have been false whereof he made mention before; neither should the Spirit have been given so much to them as to others. Again, we hear how Paul giveth thanks to God, that he speaketh with divers tongues, (1-Corinthians 14:18.) Truly he challengeth to himself both the understanding, and also the use thereof. Neither did he attain to this skill by his own study and industry, but he had it by the gift of the Spirit. In the same place he affirmeth that it is an especial gift, wherewith all men are not endued. I suppose that it doth manifestly appear hereby that the apostles had the variety and understanding of tongues given them, that they might speak unto the Greeks in Greek, unto the Italians in the Italian tongue, [2] and that they might have true communication (and conference) with their hearers. Notwithstanding, I leave it indifference whether there was any second miracle wrought or no, so that the Egyptians and Elamites did understand Peter speaking in the Chaldean tongue, as if he did utter divers voices. For there be some conjectures which persuade me thus to think, and yet not so firm but that they may be refuted. For it may be that they spoke with divers tongues, as they light upon this man or that, and as occasion was offered, and as their languages were diverse. Therefore, it was a manifest miracle, when they saw them ready to speak divers languages. As touching Peter's sermon, it might be understood of the greater part of men wheresoever they were born; for it is to be thought that many of those which came to Jerusalem were skillful in the Chaldean tongue. Again, it shall be nothing inconvenient if we say that he spoke also in other tongues. Although I will not much stand about this matter; so that this be out of doubt, that the apostles changed their speech. [3]

Footnotes

1 - "Nativum," native.

2 - "Latine," in Latin.

3 - "Vere mutasse," truly changed.

Were all filled with the Holy Ghost - Were entirely under his sacred influence and power. See the notes on Luke 1:41, Luke 1:67. To be filled with anything is a phrase denoting that all the faculties are pervaded by it, engaged in it, or under its influence, Acts 3:10, "Were filled with wonder and amazement"; Acts 5:17, "Filled with indignation"; Acts 13:45, "Filled with envy"; Acts 2:4, "Filled with joy and the Holy Spirit."
Began to speak with other tongues - In other languages than their native tongue. The languages which they spoke are specified in Acts 2:9-11.
As the Spirit gave them utterance - As the Holy Spirit gave them power to speak. This language implies plainly that they were now endued with a faculty of speaking languages which they had not before learned. Their native tongue was that of Galilee, a somewhat barbarous dialect of the common language used in Judea - the Syro-Chaldaic. It is possible that some of them might have been partially acquainted with the Greek and Latin, as each of those languages was spoken among the Jews to some extent; but there is not the slightest evidence that they were acquainted with the languages of the different nations afterward specified. Various attempts have been made to account for this remarkable phenomenon without supposing it to be a miracle. But the natural and obvious meaning of the passage is, that they were endowed by the supernatural power of the Holy Spirit with ability to speak foreign languages, and languages to them before unknown. It does not appear that each one had the power of speaking all the languages which are specified Acts 2:9-11, but that this ability was among them, and that together they could speak these languages, probably some one and some another. The following remarks may perhaps throw some light on this remarkable occurrence:
(1) It was predicted in the Old Testament that what is here stated would occur in the times of the Messiah. Thus, in Isaiah 28:11, "Withanother tongue will he speak unto this people." Compare 1-Corinthians 14:21 where this passage is expressly applied to the power of speaking foreign languages under the gospel.
(2) it was promised by the Lord Jesus that they should have this power, Mark 16:17, "These signs shall follow them that believethey shall speak with new tongues."
(3) the ability to do it existed extensively and long in the church, 1-Corinthians 12:10-11, "To another divers kinds of tongues; to another the interpretation of tongues: all these worketh that one and the self-same Spirit"; Acts 2:28, "God hath set in the churchdiversities of tongues." Compare also Acts 2:30, and Acts 14:2, Acts 14:4-6, Acts 14:9,Acts 14:13-14; Acts 14:18-19, Acts 14:22-23, Acts 14:27, Acts 14:39. From this it appears that the power was well known in the church, and was not confined to the apostles. This also may show that in the case in the Acts , the ability to do this was conferred on other members of the church as well as the apostles.
(4) it was very important that they should be endowed with this power in their great work. They were going forth to preach to all nation; and though the Greek and Roman tongues were extensively spoken, yet their use was not universal, nor is it known that the apostles were skilled in those languages. To preach to all nations, it was indispensable that they should be able to understand their language. And in order that the gospel might be rapidly propagated through the earth, it was necessary that they should be endowed with ability to do this without the slow process of being compelled to learn them. It will contribute to illustrate this to remark that one of the principal hindrances in the spread of the gospel now arises from the inability to speak the languages of the nations of the earth, and that among missionaries of modern times a long time is necessarily spent in acquiring the language of a people before they are prepared to preach to them.
(5) one design was to establish the gospel by means of miracles. Yet no miracle could be more impressive than the power of conveying their sentiments at once in all the languages of the earth. When it is remembered what a slow and toilsome process it is to learn a foreign tongue, this would I be regarded by the pagan as one of the most striking miracles which could be performed, 1-Corinthians 14:22, 1-Corinthians 14:24-25.
(6) the reality and certainty of this miracle is strongly attested by the early triumphs of the gospel. That the gospel was early spread over all the world, and that, too, by the apostles of Jesus Christ, is the clear testimony of all history. They preached it in Arabia, Greece, Syria, Asia, Persia, Africa, and Rome. Yet how could this have been effected without a miraculous power of speaking the languages used in all those places? Now, it requires the toil of many years to speak in foreign languages; and the recorded success of the gospel is one of the most striking attestations to the fact of the miracle that could be conceived.
(7) the corruption of language was one of the most decided effects of sin, and the source of endless embarrassments and difficulties, Genesis. 11: It is not to be regarded as wonderful that one of the effects of the plan of recovering people should be to show the power of God over all evil, and thus to furnish striking evidence that the gospel could meet all the crimes and calamities of people. And we may add,
(8) That from this we see the necessity now of training people who are to be missionaries to other lands. The gift of miracles is withdrawn. The apostles, by that miracle, simply were empowered to speak other languages. That power must still be had if the gospel is to be preached. But it is now to be obtained, not by miracle, but by stow and careful study and toil. If possessed, people must be taught it. And as the church is bound Matthew 28:19 to send the gospel to all nations, so it is bound to provide that the teachers who shall be sent forth shall be qualified for their work. Hence, one of the reasons of the importance of training men for the holy ministry.

To speak with other tongues - At the building of Babel the language of the people was confounded; and, in consequence of this, they became scattered over the face of the earth: at this foundation of the Christian Church, the gift of various languages was given to the apostles, that the scattered nations might be gathered; and united under one shepherd and superintendent (επισκοπος) of all souls.
As the Spirit gave them utterance - The word αποφθεγγεσθαι seems to imply such utterance as proceeded from immediate inspiration, and included oracular communications.

And they were all filled with the Holy Ghost, and began to speak with (c) other tongues, as the (d) Spirit gave them utterance.
(c) He calls them "other tongues" which were not the same as the apostles commonly used, and Mark calls them "new tongues".
(d) By this we understand that the apostles were not speaking one language and then another by chance at random, or as eccentric men used to do, but that they kept in mind the languages of their hearers: and to be short, that they only spoke as the Holy Spirit directed them to speak.

And they were all filled with the Holy Ghost,.... With the gifts of the Holy Spirit; they had received the Spirit before, as a Spirit of grace, and were endowed with great gifts; but now they had great plenty of them, a large abundance; they were like vessels filled to the brim; they were as it were covered with them; there was an overflow of them upon them; and now it was, that they were baptized with him; See Gill on Acts 1:5. Not only the twelve apostles, but the seventy disciples; and it may be all the hundred and twenty, that were together, even women as well as men: Acts 2:17.
And began to speak with other tongues; besides, and different from that in which they were born and brought up, and usually spake; they spake divers languages, one spoke one language, and another, another; and the same person spoke with various tongues, sometimes one language, and sometimes another. These are the new tongues, Christ told them they should speak with, Mark 16:17 such as they had never heard, learned, nor known before:
as the Spirit gave them utterance; they did not utter anything of themselves, and what came into their minds, things of little or no importance; nor in a confused and disorderly manner; but they were wise and weighty sentences they delivered, as the word signifies; even the wonderful works of God, Acts 2:11 the great doctrines of the Gospel; and though in different languages, yet in a very orderly and distinct manner, so as to be heard and understood by the people. The Vulgate Latin and Ethiopic versions read, "as the Holy Spirit", &c.

they . . . began to speak with . . . tongues, &c.--real, living languages, as is plain from what follows. The thing uttered, probably the same by all, was "the wonderful works of God," perhaps in the inspired words of the Old Testament evangelical hymns; though it is next to certain that the speakers themselves understood nothing of what they uttered (see on 1Co. 14:1-25).

They were all filled with the Holy Spirit. All the disciples present. To be filled implies that the human spirit within was overwhelmed by, or immersed in, the Holy Spirit. The baptism of the Spirit was not a sprinkling, but an outpouring that overwhelmed the human spirit.
Began to speak. This was the "Beginning." See Luke 24:47 and Acts 11:15.
With other tongues. In the languages of all the different countries from which Jews had come up to Pentecost. Many would be unable to understand the Hebrew dialect of Judea in that period, and hence, they must be preached to in the tongue of their own country if they understood. That the gospel on this, the first day the Great Commission was ever preached, was preached in all tongues, symbolized the fact that it is for all nations.
As the Spirit gave them utterance. They were not allowed to preach the Great Commission until now, in order that every word uttered on this day might be the word of the Spirit, not of man. The words were to be spoken to an audience, not of those in Jerusalem only, but to our whole race in all time, in order to show how sinners are to be saved under the gospel.

And they began to speak with other tongues - The miracle was not in the ears of the hearers, (as some have unaccountably supposed,) but in the mouth of the speakers. And this family praising God together, with the tongues of all the world, was an earnest that the whole world should in due time praise God in their various tongues. As the Spirit gave them utterance - Moses, the type of the law, was of a slow tongue; but the Gospel speaks with a fiery and flaming one.