Wherefore let him that speaketh in another tongue This is an anticipation, by way of reply to a question which might very readily be proposed to him. "If any one, therefore, is able to speak a foreign language, will the gift be useless? Why should that be kept back, which might be brought out to light, to the glory of God?" He shows the remedy. "Let him," says he, "ask from God the gift of interpretation also. If he is without this, let him abstain in the meantime from ostentation." [1]

Footnotes

1 - "De parler a ostentation;" -- "From speaking for ostentation's sake."

Pray that he may interpret - Let him ask of God ability that he may explain it clearly to the church. It would seem probable that the power of speaking foreign languages, and the power of conveying truth in a clear and distinct manner, were not always found in the same person, and that the one did not of necessity imply the other. The truth seems to have been, that these extraordinary endowments of the Holy Spirit were bestowed upon people in some such way as "ordinary" talents and mental powers are now conferred; and that they became in a similar sense the "characteristic mental endowments of the individual," and of course were subject to the same laws, and liable to the same kinds of abuse, as mental endowments are now. And as it now happens that one man may have a special faculty for acquiring and expressing himself in a foreign language who may not be by any means distinguished for clear enunciation, or capable of conveying his ideas in an interesting manner to a congregation, so it was then.
The apostle, therefore, directs such, if any there were, instead of priding themselves on their endowments, and instead of always speaking in an unknown tongue, which would he useless to the church, to "pray" for the more useful gift of being able to convey their thoughts in a clear and intelligible manner in their vernacular tongue. This would be useful. The truths, therefore, that they had the power of speaking with eminent ability in a foreign language, they ought to desire to be able to "interpret" so that they would be intelligible to the people whom they addressed in the church. This seems to me to be the plain meaning of this passage, which has given so much perplexity to commentators. Macknight renders it, however, "Let him who prayeth in a foreign language, pray so as some one may interpret;" meaning that he who prayed in a foreign language was to do it by two or three sentences at a time, so that he might be followed by an interpreter. But this is evidently forced. In order to this, it is needful to suppose that the phrase ὁ λαλῶν ho lalōn , "that speaketh," should be rendered, contrary to its obvious and usual meaning, "who prays," and to supply τις tis, "someone," in the close of the verse. The obvious interpretation is that which is given above; and this proceeds only on the supposition that the power of speaking foreign languages and the power of interpreting were not always united in the same person - a supposition that is evidently true, as appears from 1-Corinthians 12:10.

Pray that he may interpret - Let him who speaks or reads the prophetic declarations in the Old Testament, in that tongue in which they were originally spoken and written, pray to God that he may so understand them himself, and receive the gift of interpretation, that he may be able to explain them in all their depth and latitude to others.

Wherefore let him that speaketh in an [unknown] tongue (h) pray that he may interpret.
(h) Pray for the gift of interpretation.

Wherefore let him that speaketh in an unknown tongue,.... The Hebrew, or any other, the gift of speaking with which is bestowed upon him:
pray that he may interpret; that he may have also the gift of interpretation of tongues; for as has been before hinted, these two gifts were distinct; and a man might have the one, and not the other; a man might speak in an unknown tongue, so as to understand himself, what he said, and be edified, and yet not be capable of translating it at once into the common language of the people; and if he could not do this, he would not excel in his gift to the edification of the church; whereas if he could interpret he would, and therefore, above all things, he should pray to the Father of lights, the giver of every good and perfect gift, that he might be furnished with this also.

Explain, "Let him who speaketh with a tongue [unknown] in his prayer (or, when praying) strive that he may interpret" [ALFORD]. This explanation of "pray" is needed by its logical connection with "prayer in an unknown tongue" (1-Corinthians 14:14). Though his words be unintelligible to his hearers, let him in them pray that he may obtain the gift of interpreting, which will make them "edifying" to "the church" (1-Corinthians 14:12).

That he may be able to interpret - Which was a distinct gift.