John Chrysostom, on 1Cor 14:10

"There are, it may be, so many kinds of voices in the world, and no kind is without signification:" i. e., so many tongues, so many voices of Scythians, Thracians, Romans, Persians, Moors, Indians, Egyptians, innumerable other nations.

"If then I know not the meaning of the voice, I shall be to him that speaketh a barbarian." "For suppose not," saith he, "that this happens only in our case; rather in all one may see this taking place: so that I do not say this to disparage the voice, but to signify that to me it is useless, as long as it is not intelligible." Next, that he may not render the accusation unpalatable, he makes his charge alike for the two, saying, "He shall be unto me a barbarian, and I to him." Not from the nature of the voice, but from our ignorance. Seest thou how by little and little he draws men to that which is akin to the subject. Which is his use to do, to fetch his examples from afar, and to end with what more properly belongs to the matter. For having spoken of a pipe and harp, wherein is much that is inferior and unprofitable, he comes to the trumpet, a thing more useful; next, from that he proceeds to the very voice itself. So also before, when he was discounting to show that it was not forbidden the Apostles to receive, beginning first with husbandmen, and shepherds, and soldiers, then he brought the discourse on to that which is nearer to the subject, the priests in the old covenant.

But do thou, I pray, consider, how every where he hath given diligence to free the gift from censure, and to bring round the charge to the receivers of it. For he said not, "I shall be a barbarian," but, "unto him that speaketh, a barbarian." And again, he did not say, "he that speaketh shall be a barbarian," but "he that speaketh shall be a barbarian unto me."