After his resurrection, Jesus told his disciples that signs would accompany believers. One of those signs was that they would speak with new tongues, or other languages.

And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover.
Mark 16:17–18

The concept of prophets speaking by the Holy Spirit was well known. But those inspired words were in their own language. This was something new, and on another level.

Shortly afterward, Christ’s prophetic words were fulfilled when the Holy Spirit was poured out on the day of Pentecost. As the 120 or so disciples were filled with God’s Spirit, they began to speak in other languages as his Spirit gave them utterance.

And when the day of Pentecost was fully come, they were all with one accord in one place. And suddenly there came a sound from heaven as of a rushing mighty wind [or breath], and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
Acts 2:1–4

The occurrence gathered large crowds of people who either wondered at it or mocked. Many in the multi-national multitude recognised their own languages, and noted the disciples were speaking “the wonderful works of God”.

And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven. Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language. And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans? And how hear we every man in our own tongue, wherein we were born? Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia, Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes, Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God. And they were all amazed, and were in doubt, saying one to another, What meaneth this? Others mocking said, These men are full of new wine.
Acts 2:5-13

Why did God accompany baptism in the Spirit with speaking in new tongues? Apart from being a sign that the disciples had received the Holy Spirit, what else did it signify? What does it accomplish? Why would God give us a “fresh” or new tongue to speak in?

The connection of the heart and the tongue

In Zephaniah there is a prophecy speaking of the future state of the divided nations and Israel, when Christ returns to establish his kingdom upon the earth:

For then will I turn to the people a pure language, that they may all call upon the name of the LORD, to serve him with one consent.
Zephaniah 3:9

For then (changing their impure language) I will give to the people a clear and pure speech from pure lips, that they may all call upon the name of the Lord, to serve Him with one unanimous consent and one united shoulder (bearing the yoke of the Lord).
Zephaniah 3:9, Amplified Bible Classic

Then I will give to the peoples (clear and pure speech from) purified lips (which reflect their purified hearts), that all of them may call on the name of the Lord, to serve Him shoulder to shoulder (united).
Zephaniah 3:9, Amplified Bible

I will purify each language and make those languages acceptable for praising me. Then, with hearts united, everyone will serve only me, the LORD.
Zephaniah 3:9

The principle in this prophecy shows that God ultimately desires a pure language – pure speech and pure praise – from a pure heart. And he would have all nations, all tongues, and all hearts united in that purity.

That suggests a very good reason for the accompaniment of the baptism of the Spirit with speaking in a new and pure tongue. It reflects and signals the purification of the heart.

Speaking “the wonderful works of God” in a new tongue by the utterance of the Spirit aligns with Jesus’ principle that “out of the abundance of the heart the mouth speaketh” (see Luke 6:45). An evil heart speaks evil things: things not in accordance with the Word and thoughts of God. A good heart speaks good things: things in accordance with the Word and thoughts of God – things like “the wonderful works of God”.

As Jesus said in the same context “the tree is known by his fruit” (Matthew 12:33). The heart is revealed by the fruit of the mouth:

Either make the tree good, and his fruit good; or else make the tree corrupt, and his fruit corrupt: for the tree is known by his fruit. O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh. A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things. But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment. For by thy words thou shalt be justified, and by thy words thou shalt be condemned.
Matthew 12:33–37

God considers the heart and speech of mankind to be no longer pure. They are no longer in accord with his teaching. Man’s thoughts are not God’s thoughts. Man’s ways are not God’s ways. The word of man is not the Word of God.

There are many passages in scripture which link the corruption of the heart or mind with the tongue. The corrupt words that proceed from a defiled heart in turn defile us:

And he called the multitude, and said unto them, Hear, and understand: Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man. … Then answered Peter and said unto him, Declare unto us this parable. And Jesus said, Are ye also yet without understanding? Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught? But those things which proceed out of the mouth come forth from the heart; and they defile the man. For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies: These are the things which defile a man: but to eat with unwashen hands defileth not a man.
Matthew 15:10–20

The apostle Paul, too, made the connection.

As it is written, There is none righteous, no, not one: There is none that understandeth, there is none that seeketh after God. They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one. Their throat is an open sepulchre; with their tongues they have used deceit; the poison of asps is under their lips: Whose mouth is full of cursing and bitterness: Their feet are swift to shed blood: Destruction and misery are in their ways: And the way of peace have they not known: There is no fear of God before their eyes.
Romans 3:10–18

After declaring “there is none that doeth good, no, not one”, Paul lists a number of scripture proofs, the first four of which concern the throat, the tongue, the lips and the mouth – all referring, in God’s eyes, to the unclean, deceitful, poisonous and bitter words which we speak. If the throat is seen as an open tomb in God’s eyes, it is because it reveals a dead, corrupted heart within.

Any doubt as to the central part the tongue, as mouthpiece of the heart, plays in the defilement of the body is removed in the passage in James 3:

For in many things we offend all. If any man offend not in word, the same is a perfect man, and able also to bridle the whole body. Behold, we put bits in the horses’ mouths, that they may obey us; and we turn about their whole body. Behold also the ships, which though they be so great, and are driven of fierce winds, yet are they turned about with a very small helm, whithersoever the governor listeth. Even so the tongue is a little member, and boasteth great things. Behold, how great a matter a little fire kindleth! And the tongue is a fire, a world of iniquity: so is the tongue among our members, that it defileth the whole body, and setteth on fire the course of nature; and it is set on fire of hell. For every kind of beasts, and of birds, and of serpents, and of things in the sea, is tamed, and hath been tamed of mankind: But the tongue can no man tame; it is an unruly evil, full of deadly poison. Therewith bless we God, even the Father; and therewith curse we men, which are made after the similitude of God. Out of the same mouth proceedeth blessing and cursing. My brethren, these things ought not so to be. Doth a fountain send forth at the same place sweet water and bitter? Can the fig tree, my brethren, bear olive berries? either a vine, figs? so can no fountain both yield salt water and fresh.
James 3:2–12

The tongue of man is a destructive flame – a fire of hell, defiling and controlling the whole body. It can set fire to nations as well as individuals. It gives birth to the evil conceived within the heart, and is the fruit of its evil seed.

No man can tame it, even those who, like the prophets of old, use their language to praise God and on God’s behalf. It is a mixed fountain of good and tainted water, and cannot be made pure. While, as James indicates, we must make a diligent effort to keep our tongue under control, this is something we of ourselves can never accomplish to perfection in the flesh.

Isaiah the prophet saw a vision that not only confirms this principle, but symbolises God’s solution to it:

In the year that king Uzziah died I saw also the Lord sitting upon a throne, high and lifted up, and his train filled the temple. . . . Then said I, Woe is me! for I am undone; because I am a man of unclean lips, and I dwell in the midst of a people of unclean lips: for mine eyes have seen the King, the LORD of hosts. Then flew one of the seraphims unto me, having a live coal in his hand, which he had taken with the tongs from off the altar: And he laid it upon my mouth, and said, Lo, this hath touched thy lips; and thine iniquity is taken away, and thy sin purged. Also I heard the voice of the Lord, saying, Whom shall I send, and who will go for us? Then said I, Here am I; send me.
Isaiah 6:1–8

The immediate reaction of Isaiah to the presence and perfect holiness of God was a recognition of his own uncleanness, his sin – like a man suddenly realising he has come to a Royal Wedding in dirty rags. The prophet stood in the Light and his sin was revealed. His instinctive concern focused upon the most obvious outward manifestation of this: his unclean mouth, the door to his unclean mind.

In spite of being a prophet, Isaiah knew his words, and the words of his people, were not the pure and holy words of God. He knew he was flawed at heart like everyone else. And his mouth was the organ which most obviously proved it.

God did not disagree with Isaiah, but rather the angel took a coal of fire from the altar of sacrifice and touched his lips with it. The angel in the vision did not touch the heart, or mind, of the inner man, but, symbolically, rather touched the outward lips with this holy fire. The cleansing of the outward symbolised the cleansing of the inward.

Just as the angel took fire from the altar of sacrifice, the fire of the Holy Spirit in the New Testamant is connected with Christ’s sacrifice. The new tongues of praise the disciples received on the Day of Pentecost were not “set on fire of hell”, as James spoke of, but set on fire of the Holy Spirit, as the Spirit gave them utterance.

Isaiah’s vision helps us understand the connection between the changing of the tongue on the day of Pentecost and the changing of the heart. As God prophesied to Israel: “A new heart also will I give you, and a new spirit will I put within you” (Ezekiel 36:26). Out of the abundance of this new fresh heart, and given utterance by this new fresh Spirit, they spoke in a new fresh tongue.

Should we be surprised that in God’s miraculous plan to purify our hearts he might also take control of our tongues and purify and tame them by his Spirit?

By taking control of the tongue, God demonstrated his taming and control of the whole body – a body which became “the temple of the Holy Ghost” (1 Corinthians 6:19).

The perfect sacrifice of praise

Speaking in tongues by the Spirit of God provides us with a prayer language intended for communication with God. It is not directed at men, and it is not the fruit of our own mind or understanding:

For he that speaketh in an unknown tongue speaketh not unto men, but unto God: for no man understandeth him; howbeit in the spirit he speaketh mysteries.
1 Corinthians 14:2

For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful. What is it then? I will pray with the spirit, and I will pray with the understanding also: I will sing with the spirit, and I will sing with the understanding also.
1 Corinthians 14:14-15

God has granted those who believe on him both a pure and sealed language of worship. It is praise that cannot itself be tainted or changed by our own words or by our own thoughts.
Praise is a sacrifice to be offered to God.

By him therefore let us offer the sacrifice of praise to God continually, that is, the fruit of our lips giving thanks to his name.
Hebrews 13:15

While we can all offer up a “sacrifice of praise” in our own thoughts and language, speaking in tongues is a God-given sacrifice of praise.

In the same way that Christ was the pure sacrifice for sin provided from heaven, superior to all the offerings of man, so the utterance of the Spirit is the perfect sacrifice of praise, and the purified fruit of our lips.

When we become the “temple of the Holy Spirit”, that pure sacrifice of praise is offered up by the Spirit himself.

Jesus said that God’s temple was intended to be a house of prayer for all nations.

Is it not written, My house shall be called of all nations the house of prayer?
Mark 11:17

What better sign of the Spirit coming to dwell within God’s house of prayer, or the temple of our body, than a miraculous and God-given prayer? And what better sign than one that represents the languages and prayers of all nations?

For the Spirit of “grace” is also the Spirit of “supplications”, or earnest prayer (Zechariah 12:10). And God desires us to supplicate him in the Spirit.

Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints;
Ephesians 6:18

But ye, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost,
Jude 1:20

And how appropriate that the “pure language” that God has prophesied for all nations, that they may “all call upon the name of the LORD, to serve him with one consent” should be foreshadowed in the unifying outpouring of the Spirit on the day of Pentecost, in the tongues of men from “every nation under heaven”, as a counterpoint to the division of the world in the confusion of languages at the tower of Babel.

For the sign of many different Gentile tongues spoken at Pentecost by the Jews was also a sign that salvation under the New Covenant of the Spirit was not to the Jews only, but to all the world. And that his greater temple, the body of Christ, should be a house of prayer for all nations.

After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands;
Revelation 7:9

The record of the book of Acts demonstrates that baptism in the Holy Spirit was always accompanied by speaking in tongues. It is an appropriate, visible, and supernatural seal of God’s pledge upon those who are “sealed with that holy Spirit of promise”. God had good reason for it, and Christ’s disciples all had this experience. You can too.

This Jesus hath God raised up, whereof we all are witnesses. Therefore being by the right hand of God exalted, and having received of the Father the promise of the Holy Ghost, he hath shed forth this, which ye now see and hear.
Acts 2:32-33

Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.
Acts 2:38-39