Cross reference
1 Corinthians 14:19
19 howbeit in the church I had rather speak five words with my understanding, that I might instruct others also, than ten thousand words in a tongue.
1 Corinthians 14:21-22
21 In the law it is written, By men of strange tongues and by the lips of strangers will I speak unto this people; and not even thus will they hear me, saith the Lord.
22 Wherefore tongues are for a sign, not to them that believe, but to the unbelieving: but prophesying `is for a sign', not to the unbelieving, but to them that believe.
1 Corinthians 14:4
4 He that speaketh in a tongue edifieth himself; but he that prophesieth edifieth the church.