1 Corinthians 14:21-22

21This is written in the Bible: ‘I will send strangers to speak to my people. They will speak my message to them in strange languages. But even when I do this, my people will not listen to me.’ That is what the Lord God has said.

22So the gift to speak in different languages is like a sign. It shows God's power to people who do not believe in him. It is not a sign to help believers. But the gift to speak clear messages from God shows his power to believers. It is not a sign for those people who do not believe.