1 Corinthians 14:11 (ESV)

11 but if I do not know the meaning of the language, I will be a foreigner to the speaker and the speaker a foreigner to me.

The Greek word translated as foreigner is barbaros (from which the word barbarian is derived). It was used to refer to all non-Greeks (people who did not adopt the Greek language and culture).

When people cannot understand each other’s language, there exists a barrier between them. This is also true when some people in the church speak in languages that are neither understood nor interpreted. Rather than building up the church, the wrong use of tongues will create division.

The phrase translated as the meaning of the language is literally the power of the language. If a language is not understood, its power is lost.