John Chrysostom, on 1Cor 14:16

"Else," saith he, "if thou bless with the spirit, how shall he that filleth the place of the unlearned say the Amen at thy giving of thanks, seeing he knoweth not what thou sayest?"

"For thou verily givest thanks well, but the other is not edified."

Observe how again here he brings his stone to the plumb-line every where seeking the edification of the Church. Now by the "unlearned" he means the laymen, and signifies that he also suffers no little loss when he is unable to say the Amen. And what he saith is this: "if thou shalt bless in a barbarian tongue, not knowing what thou sayest, nor able to interpret, the layman cannot respond the Amen. For not hearing the words, 'forever and ever,' which are at the end, he doth not say the Amen." Then again, comforting him concerning this, that he might not seem to hold the gift too cheap; the same kind of remark as he made above, that "he speaketh mysteries," and "speaketh unto God," and "edifieth himself," and "prayeth with the spirit," intending no little comfort from these things, this also he utters here, saying, "for thou indeed givest thanks well," since thou speakest being moved by the Spirit: but the other hearing nothing nor knowing what is said, stands there, receiving no great advantage by it.