Be Not Children In Understanding

1 Corinthians 14:

20 Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men.
21 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.
22 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.

1 Cor.14:20-22