Filled With The Holy Spirit.
And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance. Acts 2:4 NKJV
Here is a visible sign of the gift they were to receive. They saw cloven tongues, like as of fire, and it sat-ekathise, not they sat, those cloven tongues, but he, that is the Spirit (signified thereby), rested upon each of them, as he is said to rest upon the prophets of old. Or, as Dr. Hammond describes it, "There was an appearance of something like flaming fire lighting on every one of them, which divided asunder, and so formed the resemblance of tongues, with that part of them that was next their heads divided or cloven." The flame of a candle is somewhat like a tongue; and there is a meteor which naturalists call ignis lambens-a gentle flame, not a devouring fire; such was this. Observe,
There was an outward sensible sign, for the confirming of the faith of the disciples themselves, and for the convincing of others. Thus the prophets of old had frequently their first mission confirmed by signs, that all Israel might know them to be established prophets.
The sign given was fire, that John Baptist's saying concerning Christ might be fulfilled, He shall baptize you with the Holy Ghost and with fire; with the Holy Ghost as with fire. They were now, in the feast of Pentecost, celebrating the memorial of the giving of the law upon mount Sinai; and as that was given in fire, and therefore is called a fiery law, so is the gospel. Ezekiel's mission was confirmed by a vision of burning coals of fire (ch. 1:13), and Isaiah's by a coal of fire touching his lips, ch. 6:7. The Spirit, like fire, melts the heart, separates and burns up the dross, and kindles pious and devout affections in the soul, in which, as in the fire upon the altar, the spiritual sacrifices are offered up. This is that fire which Christ came to send upon the earth. Luke 12:49.
This fire appeared in cloven tongues. The operations of the Spirit were many; that of speaking with divers tongues was one, and was singled out to be the first indication of the gift of the Holy Ghost, and to that this sign had a reference. They were tongues; for from the Spirit we have the word of God, and by him Christ would speak to the world, and he gave the Spirit to the disciples, not only to endue them with knowledge, but to endue them with a power to publish and proclaim to the world what they knew; for the dispensation of the Spirit is given to every man to profit withal. These tongues were cloven, to signify that God would hereby divide unto all nations the knowledge of his grace, as he is said to have divided to them by his providence the light of the heavenly bodies, Deuteronomy 4:19. The tongues were divided, and yet they still continued all of one accord; for there may be a sincere unity of affections where yet there is a diversity of expression. Dr. Lightfoot observes that the dividing of tongues at Babel was the casting off of the heathen; for when they had lost the language in which alone God was spoken of and preached, they utterly lost the knowledge of God and religion, and fell into idolatry. But now, after above two thousand years, God, by another dividing of tongues, restores the knowledge of himself to the nations.
This fire sat upon them for some time, to denote the constant residence of the Holy Ghost with them. The prophetic gifts of old were conferred sparingly and but at some times, but the disciples of Christ had the gifts of the Spirit always with them, though the sign, we may suppose, soon disappeared. Whether these flames of fire passed from one to another, or whether there were as many flames as there were persons, is not certain. But they must be strong and bright flames that would be visible in the day-light, as it now was, for the day was fully come.
What was the immediate effect of this? They were all filled with the Holy Ghost, more plentifully and powerfully than they were before. They were filled with the graces of the Spirit, and were more than ever under his sanctifying influences-were now holy, and heavenly, and spiritual, more weaned from this world and better acquainted with the other. They were more filled with the comforts of the Spirit, rejoiced more than ever in the love of Christ and the hope of heaven, and in it all their griefs and fears were swallowed up. They were also, for the proof of this, filled with the gifts of the Holy Ghost, which are especially meant here; they were endued with miraculous powers for the furtherance of the gospel. It seems evident to me that not only the twelve apostles, but all the hundred and twenty disciples were filled with the Holy Ghost alike at this time-all the seventy disciples, who were apostolic men, and employed in the same work, and all the rest too that were to preach the gospel; for it is said expressly (Ephesians 4:8, 11), When Christ ascended on high (which refers to this, v. 33), he gave gifts unto men, not only some apostles (such were the twelve), but some prophets and some evangelists (such were many of the seventy disciples, itinerant preachers), and some pastors and teachers settled in particular churches, as we may suppose some of these afterwards were. The all here must refer to the all that were together, v. 1; ch. 1:14, 15. 2. They began to speak with other tongues, besides their native language, though they had never learned any other. They spoke not matters of common conversation, but the word of God, and the praises of his name, as the Spirit gave them utterance, or gave them to speak apophthengesthai-apophthegms, substantial and weighty sayings, worthy to be had in remembrance. It is probable that it was not only one that was enabled to speak one language, and another another (as it was with the several families that were dispersed from Babel), but that every one was enabled to speak divers languages, as he should have occasion to use them. And we may suppose that they understood not only themselves but one another too, which the builders of Babel did not, Genesis 11:7. They did not speak here and there a word of another tongue, or stammer out some broken sentences, but spoke it as readily, properly, and elegantly, as if it had been their mother-tongue; for whatever was produced by miracle was the best of the kind. They spoke not from any previous thought or meditation, but as the Spirit gave them utterance; he furnished them with the matter as well as the language. Now this was, A very great miracle; it was a miracle upon the mind (and so had most of the nature of a gospel miracle), for in the mind words are framed. They had not only never learned these languages, but had never learned any foreign tongue, which might have facilitated these; nay, for aught that appears, they had never so much as heard these languages spoken, nor had any idea of them. They were neither scholars nor travellers, nor had had any opportunity of learning languages either by books or conversation. Peter indeed was forward enough to speak in his own tongue, but the rest of them were no spokesmen, nor were they quick of apprehension; yet now not only the heart of the rash understands knowledge, but the tongue of the stammerers is ready to speak eloquently, Isaiah 32:4. When Moses complained, I am slow of speech, God said, I will be with thy mouth, and Aaron shall be thy spokesman. But he did more for these messengers of his: he that made man's mouth new-made theirs. (2.) A very proper, needful, and serviceable miracle. The language the disciples spoke was Syriac, a dialect of the Hebrew; so that it was necessary that they should be endued with the gift, for the understanding both of the original Hebrew of the Old Testament, in which it was written, and of the original Greek of the New Testament, in which it was to be written. But this was not all; they were commissioned to preach the gospel to every creature, to disciple all nations. But here is an insuperable difficulty at the threshold. How shall they master the several languages so as to speak intelligibly to all nations? It will be the work of a man's life to learn their languages. And therefore, to prove that Christ could give authority to preach to the nations, he gives ability to preach to them in their own language. And it should seem that this was the accomplishment of that promise which Christ made to his disciples (John 14:12), Greater works than these shall you do. For this may well be reckoned, all things considered, a greater work than the miraculous cures Christ wrought. Christ himself did not speak with other tongues, nor did he enable his disciples to do so while he was with them: but it was the first effect of the pouring out of the Spirit upon them. And archbishop Tillotson thinks it probable that if the conversion of infidels to Christianity were now sincerely and vigorously attempted, by men of honest minds, God would extraordinarily countenance such an attempt with all fitting assistance, as he did the first publication of the gospel. - Matthew Henry