A supernatural ability the Holy Spirit gives to certain people to speak in a known language they have not learned for the purpose of evangelism, exhortation and praising God. In some cases, the language being spoken requires interpretation to accomplish this purpose.
Biblical References:
Acts 2:4-13
Acts 10:45-46
Acts 19:1-6
1 Corinthians 12:10
1 Corinthians 14:13-19, 26-28
Gift Characteristics:
Differs from our personal prayer language.... The gift of tongues, along with the other eight gifts mentioned in 1 Corinthians 12:8-10, are given for "the common good". That is to say, they are spoken to other people as a message from God. However, the language one receives after being baptized in the Holy Spirit may not be used as a public message but for personal edification. Paul says this tongue speaks to God, not to other people (1 Cor. 14:2), and explains how he uses his personal prayer language in a private setting (1 Cor. 14:18-19).
May or may not be a known language.... On the day of Pentecost the disciples were baptized in the Holy Spirit and spoke in languages that were understood by those nearby (Acts 2:4-13). The Bible describes how people from different countries heard these early believers praising God in their own language. This was a sign to them that something supernatural was occurring because the disciples were unlearned in these languages. However, in 1 Corinthians 14 Paul talks about tongues needing interpretation. This indicates that the gift of tongues can also be spoken in a language that is not understand by its listener(s). In this case, the gift of tongues must be interpreted in order to have any meaning or benefit to it (1 Cor. 14:6).
Are to be commonly expected.... In 1 Corinthians 14:26 Paul says the gift of tongues should be a regular occurrence in the Church. Like prophecy, tongues serve as a way for God to communicate directly with His people. When Paul rebukes the Corinthians on the issue of tongues, it is not for exercising this gift in their church gatherings, but for misusing the gift of tongues by not providing appropriate interpretation.
Should be regulated in corporate gatherings.... Paul provides specific instructions on the use of tongues in corporate gatherings. In 1 Corinthians 14:27-28 he states that the number of "messages in tongues" at a public meeting should not exceed three, and each message should be spoken one at a time with an interpretation following it. He also says that if no one is given the gift of interpretation, then the gift of tongues should not be exercised at all. In verse 33 Paul explains his purpose in these regulations is not to suffocate or suppress the operation of tongues, but to maintain church order and allow for other gifts of the Spirit to be exercised.
Are a sign to unbelievers.... In 1 Corinthians 14:21-22 Paul uses Isaiah 28:11 as the basis for viewing tongues as a sign for unbelievers. According to this passage, tongues are not given to unbelievers for the purpose of providing guidance or encouragement (as with believers), but to be a sign to them that God is present. Hearing a message in tongues brings them face to face with the supernatural, especially when it is a language that is known by them. It also reveals their separation from God by demonstrating their inability to understand or communicate with Him.