The context of the verse in question is that the Lord Jesus had died, been buried, risen from the dead, and was about to ascend to His Father. Let us read Mark 16:14-20. “Afterward He appeared to the eleven themselves as they were reclining at the table; and He reproached them for their unbelief and hardness of heart, because they had not believed those who had seen Him after He had risen. And He said to them, ‘Go into all the world and preach the gospel to all creation. He who has believed and has been baptized shall be saved; but he who has disbelieved shall be condemned. These signs will accompany those who have believed: in My name they will cast out demons, they will speak with new tongues; they will pick up serpents, and if they drink any deadly poison, it will not hurt them; they will lay hands on the sick, and they will recover.’ So then, when the Lord Jesus had spoken to them, He was received up into heaven and sat down at the right hand of God. And they went out and preached everywhere, while the Lord worked with them, and confirmed the word by the signs that followed.” (NASB).

There is much that could be said about these verses but let us focus our attention on the question at hand. “They will speak with new tongues” in verse 17 is a prophetic statement from the Lord Jesus. An example of the fulfillment of this prophecy is in Acts 2:4-11. The setting is the day of Pentecost when the Holy Spirit came to indwell all believers. “And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit was giving them utterance. Now there were Jews living in Jerusalem, devout men from every nation under heaven. And when this sound occurred, the crowd came together, and were bewildered because each one of them was hearing them speak in his own language. They were amazed and astonished, saying, ‘Why, are not all these who are speaking Galileans? And how is it that we each hear them in our own language to which we were born? Parthians and Medes and Elamites, and residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia, Egypt and the districts of Libya around Cyrene, and visitors from Rome, both Jews and proselytes, Cretans and Arabs—we hear them in our own tongues speaking of the mighty deeds of God’” (NASB).

These verses make it clear that the Holy Spirit empowered the apostles to speak “of the mighty deeds of God” (verse 11) in other languages. This answers the question from Mark 16:17 about “new tongues.” The new tongues were actual languages that were new to the apostles. They were not brand-new languages that no one had ever spoken previously. The apostles had not studied these languages. It was a miracle that the Holy Spirit enabled them to share the good news of Christianity in languages that were new to them so that many people could hear the gospel in their own language. Noticing how the Lord worked in the early days of the Church reminds me of Psalm 107:21. “Oh that men would praise the Lord for His goodness, and His wonderful works to the children of men!”  (DJ)  (680.5)