What does the Bible say about speaking in tongues?
Intriguing example from the book of Numbers
What happened on the day of Pentecost following Jesus’s resurrection
Philipp preaching to the Samaritans
The Ordination of Israelite Elders
Numbers 11:16-17 So the LORD said to Moses: “Gather to Me seventy men of the elders of Israel, whom you know to be the elders of the people and officers over them; bring them to the tabernacle of meeting, that they may stand there with you.  Then I will come down and talk with you there. I will take of the Spirit that is upon you and will put the same upon them; and they shall bear the burden of the people with you, that you may not bear it yourself alone.
Moses was to bring 70 men to the tabernacle of meeting to consecrate them for a special task. In particular, they were to help Moses bear the burden of leadership by helping settle disputes between Israelites. When they are consecrated, God promises to “take of the Spirit that is upon you and will put the same upon them” — the same gift Moses was given to help lead the people would be distributed to these men.
The consecration happens a few verses later in Numbers 11:24-25,
“So Moses went out and told the people the words of the LORD, and he gathered the seventy men of the elders of the people and placed them around the tabernacle.  Then the LORD came down in the cloud, and spoke to him, and took of the Spirit that was upon him, and placed the same upon the seventy elders; and it happened, when the Spirit rested upon them, that they prophesied, although they never did so again.”
As promised, the Lord “took of the Spirit that was upon (Moses) and placed the same upon the seventy elders.” When “the Spirit rested upon them…they prophesied”: judging by the context, the gift of prophecy was a sign to show that the Spirit had in fact fallen upon them. Because it was a sign for this purpose, it was a temporary effect — Moses tells us, “they never (prophesied) again. So the giving of the Spirit was accompanied by a sign which confirmed the giving of the Spirit.
Pentecost and Cornelius
Acts 2:1-4, “When the Day of Pentecost had 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, and it filled the whole house where they were sitting.  Then there appeared to them divided tongues, as of fire, and one sat upon each of them.  And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance.”
On a Sunday morning, fifty days after the Passover on which Jesus was crucified, the apostles were gathered together in one place. While gathered together, the Spirit fell upon them and they began to speak in tongues — speaking in tongues is another way of saying speaking in a foreign language. We go on to learn that the sound of the mighty rushing wind gathered a crowd, they heard the apostles speaking in languages from all over the Roman Empire and they wonder what is going on.
Peter informs the multitude that what they have witnessed fulfills a prophecy from Joel, specifically that God “will pour out (His) Spirit.” Peter declares Jesus rose from the dead and upon taking His seat at the right hand of God, Jesus has poured out the Spirit. How do the multitudes know the Spirit has been poured out?
Acts 2:33, “Therefore being exalted to the right hand of God, and having received from the Father the promise of the Holy Spirit, He poured out this which you now see and hear.”
The speaking in tongues witnessed by the multitudes was evidence of God pouring out His Spirit. Or, to put it another way, like the elders in the time of Moses prophesied upon receiving the Spirit, the apostles spoke in new languages upon receiving the Spirit. Speaking in tongues was a sign that the Holy Spirit had been poured out.
This happens a second time in Acts 10:44-46 when Peter preaches the gospel to the household of Cornelius, a Gentile household. This was the first time the gospel was preached to the Gentiles. While Peter spoke, “the Holy Spirit fell upon all those who heard the word,” (verse 44) and those Jews who came with Peter were astonished because “they heard (the Gentiles) speak with tongues and magnify God” (verse 46). Later, when Peter is asked about the incident, he acknowledges the speaking in tongues to be a sign from God and (Acts 11:15-17), and those who heard his testimony agreed:
Acts 11:18, “When they heard these things they became silent; and they glorified God, saying, ‘Then God has also granted to the Gentiles repentance to life.’”
So Peter and his fellow Jewish believers interpreted the speaking in tongues as a sign that God welcomed the Gentiles to receive salvation.
These two incidents in the book of Acts indicate that tongues were interpreted as a sign that the Holy Spirit had been poured out, first on the apostles, then upon the Gentiles of Cornelius’s house.
Philip in Samaria
In Acts 8, as Saul begins leading the first persecution, the church scatters in every direction, preaching the gospel as they go; included in this group was Philipp.
Philip is the first one to preach Jesus risen from the dead in Samaria and the Samaritans, who are part Jew, receive him gladly. Philip not only preaches the gospel, but he is also able to perform exorcisms as well as healing the paralyzed. Among those who heard Philip was a man named Simon who practiced sorcery; he believed and, along with many other men and women, was baptized. So many believed in Jesus at the preaching of Philip and were baptized for the remission of sins.
Word of what is happening in Samaria reaches the apostles in Jerusalem; they dispatched Peter and John to go to Samaria. Luke tells us in Acts 8:15-17 that Peter and John,
“prayed for (the Samaritan believers) that they might receive the Holy Spirit.  For as yet He had fallen upon none of them. They had only been baptized in the name of the Lord Jesus.  Then they laid hands on them, and they received the Holy Spirit,”
Notice, they believed and were baptized but did not receive the Holy Spirit until the apostles, Peter and John, laid their hands on the people. The aforementioned Simon “saw that through the laying on of the apostles’ hands the Holy Spirit was given” (8:18) and offered money to purchase the gift of being able to give the Holy Spirit to anyone. So the apostles laid hands on believers in Jesus and were able to give the Holy Spirit.
The exact meaning of what took place in Samaria is clarified in Acts 19. Paul finds disciples in Ephesus and discovers they have not been baptized in the name of Jesus Christ; so he re-baptized them. When they had received the correct baptism, “Paul (lays) hands on them, the Holy Spirit came upon them, and they spoke with tongues and prophesied” (Acts 19:6).
As in the case with Peter and John in Samaria, Paul laid his hands on newly baptized believers, the Holy Spirit came upon them, and they spoke in tongues. Speaking in tongues was a sign that believers had received miraculous power from the Holy Spirit through the laying of the apostles’ hands.
What does the Bible say about speaking in tongues? Like the elders in Numbers who prophesied upon receiving the Spirit, tongues were a sign that believers in God had received the Holy Spirit. Speaking in tongues signaled the apostles had received the Holy Spirit and that God opened the door for salvation to the Gentiles of Cornelius’s household. The apostles could pass this gift along by laying their hands on baptized believers — Peter, John, and Paul all demonstrate that this gift was not given independently of the apostles. THIS IS THE CRUCIAL POINT: nowhere in the New Testament do we find the gift of tongues given without either an apostle present or in a situation where an apostle has not visited. Therefore, I conclude that since we no longer have apostles among us, we no longer have the gift of tongues.