What does it mean that tongues are a sign for unbelievers (1 Corinthians 14:22)?

In his first letter to the Corinthians, the apostle Paul states that speaking in tongues was “a sign, not for believers but for unbelievers” (1 Corinthians 14:22). This indicates that tongues—speaking in a language never learned by the speaker—served to catch the attention of those who did not follow Jesus Christ. Specifically, it is a sign of judgment. Paul explains that the unbelievers’ hardheartedness reflected their separation from God, much like Israel’s response to God in Isaiah’s day:

Paul warns the Corinthians against misusing tongues in the church service. The gathering of believers has no need of the sign for unbelievers. Rather than serving as a means of edification, the chaotic expression of the gift of tongues would only reinforce unbelief and confusion (1 Corinthians 14:20, 23). Paul urges the church to mature in their understanding, recognizing that tongues are not for self-glorification but have a specific purpose as a sign of judgment for unbelievers.

Of course, speaking in tongues was a gift from God and therefore a blessing, even as it functioned as a sign of judgment for unbelievers. This kind of two-fold significance has biblical precedent. For instance, the global flood rescued Noah and his family from a deeply corrupt population, yet the same water judged the wicked. Similarly, the prophesied Day of the Lord, which is still to come, has a dual meaning. It will be a day of salvation for believers but also a day of fear and judgment for unbelievers (Joel 2:31–32; Malachi 4:1–2; 1 Thessalonians 5:2–3; 2 Peter 3:10–12).

The Day of Pentecost provides a key example of how tongues functioned as a sign. On this momentous day, the followers of Jesus were baptized with the Holy Spirit. As a result, “all of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them” (Acts 2:4). When a crowd gathered, they were amazed to hear the disciples distinctly speaking to them in languages the disciples could not have known (verses 5–12). Peter explained by quoting from a prophetic passage of judgment:

The Jews in Jerusalem who heard Peter and the other disciples speaking in tongues were being given a warning: judgment was coming. The Day of the Lord was approaching, and tongues were the sign. The arrival of the Holy Spirit was the beginning of the last age, in fulfillment of God’s promises. Now is the time to repent and turn to the Lord Jesus. Today is the day of salvation.