1 Corinthians 14:18-22

I thank my God, I speak with tongues more than ye all:

Yet in the church I had rather speak five words with my understanding, that by my voice I might teach others also, than ten thousand words in an unknown tongue.

Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men.

In the law it is written, With men of other tongues and other lips will I speak unto this people; and yet for all that will they not hear me, saith the Lord.

Wherefore tongues are for a sign, not to them that believe, but to them that believe not: but prophesying serveth not for them that believe not, but for them which believe.