1st Corinthians 14:17

14 for if I pray in an [unknown] tongue, my spirit doth pray, and my understanding is unfruitful.

15 What then is it? I will pray with the spirit, and I will pray also with the understanding; I will sing psalms with the spirit, and I will sing psalms also with the understanding;

16 since, if thou mayest bless with the spirit, he who is filling the place of the unlearned, how shall he say the Amen at thy giving of thanks, since what thou dost say he hath not known?

17 for thou, indeed, dost give thanks well, but the other is not built up!

18 I give thanks to my God -- more than you all with tongues speaking --

19 but in an assembly I wish to speak five words through my understanding, that others also I may instruct, rather than myriads of words in an [unknown] tongue.

20 Brethren, become not children in the understanding, but in the evil be ye babes, and in the understanding become ye perfect;