"Is "speaking in tongues" biblical?"
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Question:  

Is it biblical to speak in tongues? Some say speaking in tongues was just for the Israelites, for a sign to them so they would believe, and that it does not apply to us now.
Response: 
Tongues is a particular gift of the Holy Spirit (1Cor.12:10), and was complemented in the early Church by the gift of "interpreting" tongues (1Cor.14:27-28). The first instance of the functioning of this gift was by the believers gathered together at Pentecost following our Lord's resurrection who all began to "speak in tongues" when the Spirit came upon them (Acts 2:1-4). This event caught the attention of all the expatriate Jews gathered in Jerusalem who heard the gospel in their own language. So it is clear from what happened at this first post-resurrection Pentecost, and from what Paul has to say on the subject of tongues in 1st Corinthians chapter 14, that a "tongue" is always a real, human language (in fact, the word glossa in Greek, from which we get "glossary", more often than not refers to a spoken language – we use "tongue" in that sense in English too of course). 
One thing to establish right at the outset, therefore, is that anyone who is "speaking in a tongue" as a result of being gifted by the Holy Spirit to do so, is, if genuinely doing so, speaking in an actual language, a language, moreover, which any native speaker could understand perfectly well. That is to say, genuine, biblical "speaking in tongues" is not gibberish or nonsensical or in anyway an unintelligible combination of sounds (for those who are able to speak and understand the language in question):
Even in the case of lifeless things that make sounds, such as the flute or harp, how will anyone know what tune is being played unless there is a distinction in the notes? Again, if the trumpet does not sound a clear call, who will get ready for battle? So it is with you. Unless you speak intelligible words with your "tongue", how will anyone know what you are saying? You will just be speaking into the air. Undoubtedly there are all sorts of languages in the world, yet none of them is without meaning.
1st Corinthians 14:7-10 NIV
In light of the above, an example of biblical "speaking in tongues" would be if you or I were to be given by the Spirit the ability to speak, say, Turkish, although we had never heard the language before nor studied it in any way. On the other hand, biblical "speaking in tongues" would not be for you or I to pour forth a series of sounds which are not a spoken human language, which have no "distinction" as Paul says above, just because we are under the influence of a highly charged emotional state. The gift of tongues is not and never was "chanting" or anything of the sort. Rather, "tongues" was always a gift of communication, designed for giving of the gospel directly to those of a different language group or for the  communication of the Word of God to a local assembly of believers (where there was also someone present with the gift of interpreting tongues). 
So in the present day, it would, theoretically, be a very simple matter to discover whether or not someone is really "speaking in a tongue" according to what the Bible says is legitimate. Let me say that I personally know of no instance where what passes for "tongues" as it is presently practiced in some groups is actually a case of someone speaking forth an intelligible stream of words in a real human language which is understandable to those who do speak that real language, but one which the speaker-in-tongues does not understand (i.e., if I were to pray out-loud in another language I have studied extensively like biblical Hebrew, reciting a Psalm I had memorized, for example, that might sound like "speaking in tongues", but it would not be true "tongues").
Please do not misunderstand: we do not doubt the power of God. All things, indeed, are possible with Him, and, of a truth, in the early Church the gift of tongues was a common and important gift which was apparently being liberally distributed by the Holy Spirit – but it was not a universal one. Not everyone spoke in tongues, even in the early Church:
Now you are the body of Christ, and each one of you is a part of it. And in the church God has appointed first of all apostles, second prophets, third teachers, then workers of miracles, also those having gifts of healing, those able to help others, those with gifts of administration, and those speaking in different kinds of tongues. Are all apostles? Are all prophets? Are all teachers? Do all work miracles? Do all have gifts of healing? Do all speak in tongues? Do all interpret?
1st Corinthians 14:27-30 NIV
So just because God can do something or has done something in the past does not mean that He is doing it now, no matter how much we may want this to be the case. God has spoken directly to certain men in the past, appointing them prophets and commissioning them to proclaim His Word and to be instruments for writing it down in inspired form (for example, Isaiah: Is.6; and Ezekiel: Ezek.2). That does not mean that He has done so in my case or in your case (the Bible, after all, is now complete – no more chapters are being added, and no one else is being commissioned by God to write more of it). It is the same for tongues. Certain gifts were extremely important in the early Church, when there was as yet no collected New Testament, no stabilized Church organization, no system of education for the preparation of teachers. In the first century, the gifts of apostleship, healing, miracles, tongues, interpretation, etc. were of great importance in establishing the incipient Church of Jesus Christ. But it is easy to understand why they are not (apparently) functioning today: we have the Bible and men to teach it, a situation which is in truth most blessed and not to be exchanged for any number of miraculous gifts:
Love never falls [into inactivity]. But whether [we are talking about gifts of] prophecy, they will cease, or about [gifts of] tongues, they will come to a stop, or [about the gift of] knowledge, it will be done away with. For when we exercise the gift of knowledge, its results are only partial. And when we exercise the gift of prophecy, its results are only partial. But when what is complete shall have come on the scene (i.e., the fully functioning Church with a complete Bible), all partial measures shall be done away with.
1st Corinthians 13:8-10
Most of the peoples of the world now have the gospel, the entire Bible, in fact, written and available in their own language; most churches have available to them the teaching of prepared men (even if this option is largely going unexercised in today's Church). In the last days before the return of our Lord, many miraculous events have been prophesied to occur (Joel 2:28-32; please see the link, "Coming Tribulation", for more information on the end times). The fact that the gift of tongues is currently in hiatus does not mean that this will ever be the case. But we seek God's truth, not men's claims, men's desires. The circumstances which made "tongues" of such critical importance in the first century no longer apply today (just as there were no more apostles appointed by the Lord after the original twelve had completed their work). Therefore it does not seem unreasonable to say that the burden of proof lies with those who suggest that they or others are now truly "speaking in tongues" – an easy enough thing to prove, if true, given that they would then be speaking a known and verifiable human language of which they have no prior or independent knowledge.
I have written quite a lot about this subject, and I invite you to have a look at the following links where more details on this and the closely related issue of the baptism of the Holy Spirit are addressed:
Tongues:  Does no man understand?
Is "speaking in tongues" a sin? 
Tongues and Healing.
The baptism of the Holy Spirit as distinct from speaking in tongues.
All Things Charismatic.
An Extended Conversation about the Baptism of the Holy Spirit 

"The baptism which now saves you": 1st Peter 3:21 

Confession of Sin, Fellowship, and the Filling of the Holy Spirit 

Is water baptism required for Christians today? 

How does being "slain in the Spirit" relate to being baptized in the Spirit? 

Sin, Baptism, Resurrection and the Book of Revelation 

Being Born Again and Baptism 

Baptism and Salvation 
 
Yours in Him who is the Truth, our dear Lord and Savior Jesus Christ.
Bob Luginbill
http://ichthys.com