We find that the scripture shows us that it did occur, but how can a Christian tell if 'Speaking in Tongues' is being given by the Holy Spirit or it has come by a false spirit. Just because a person starts to mutter, mumble or shout unknown 'words' doesn't necessarily mean that they are being given them by the Holy Spirit. People with dementia, or drunks and the insane mumble and shout unknown words, are they being given spiritual gifts of speaking in tongues. Of course not, so how can one tell if the source is from the Holy Spirit, or from another origin.
There are many references to speaking in tongues in the Bible, and we find the most about tongues are Acts 2 and I Corinthians 12-14. Now, you have to understand that at the time there were Jews and non-Jews who came to Jerusalem and from nearby regions who spoke another languages. To communicate with others with different languages, the early Christians needed to have been given a gift so they could understand the Gospel, and the scripture clearly shows that happening. There are many times being able to speak to others in their own tongue or language was very important as we see in the instance when Paul addressed the Jews to give them a understanding of who he was.
Acts 22
1 Men, brethren, and fathers, hear ye my defence which I make now unto you.
2 (And when they heard that he spake in the Hebrew tongue to them, they kept the more silence: and he saith,)
3 I am verily a man which am a Jew, born in Tarsus, a city in Cilicia, yet brought up in this city at the feet of Gamaliel, and taught according to the perfect manner of the law of the fathers, and was zealous toward God, as ye all are this day.
Now in Acts 2 when the Apostles speak in tongues it makes if very clear why and what they were speaking.
Acts 2
1 And when the day of Pentecost was fully come, they were all with one accord in one place.
2 And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting.
3 And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
4 And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
5 And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven.
The key part here is there were coming to Jerusalem, 'Jews, devout men, out of every nation under heaven.' We clearly see the purpose and the actual use of speaking in tongues, it was not just babbling or muttering of foolish nonsense, it had a specific purpose and directed for the understanding of those from other languages and lands, as they heard 'speak in our tongues the wonderful works of God.'
6 Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language.
7 And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans?
8 And how hear we every man in our own tongue, wherein we were born?
9 Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia,
10 Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes,
11 Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God.
So speaking nonsensical words and utterances with no one to understand or for no practical reason, is it spiritually the same as the speaking in tongues given to the apostles and the early church.
Keep in mind it happened in the early church, the deception of Montanism known by its adherents as the 'New Prophecy', and its followers claimed the inspiration of the Holy Spirit. They spoke in ecstatic visions and utterances and claimed they received the prophetic gift from the prophets. It originated in Phrygia, and spread rapidly to other regions in the Roman Empire and persisted in some isolated places into the 6th century. It was a false speaking in tongues, and was recognized as such, yet spread everywhere and fooled many Christians till it was stamped out.
