Wherefore, brethren This is the conclusion in connection with the principal question -- that prophecy is to be preferred to other gifts, because it is the most useful gift of all, while at the same time other gifts ought not to be despised. We must observe, however, his manner of speaking. For he intimates, that prophecy is worthy of being eagerly and ardently aspired at by all. In the meantime, he exhorts them not to envy others the rarer gift, [1] which is not so much to be desired; nay more, to allow them the praise that is due to them, divesting themselves of all envy.

Footnotes

1 - "Autres, qui ont le don des langues, qui est vn don plus rare;" -- "Others, who have the gift of tongues, which is a rarer gift."

Covet to prophesy - See the note at 1-Corinthians 14:1. This is the "summing up" of all that he had said. It was "desirable" that a man should wish to be able to speak, under the teaching of the Holy Spirit, in such a manner as to edify the church.
And forbid not - Do not suppose that the power of speaking foreign languages is useless, or is to be despised, or that it is to be prohibited. "In its own place" it is a valuable endowment; and on proper occasions the talent should be exercised; see in 1-Corinthians 14:22.

Covet to prophesy - Let it be your endeavor and prayer to be able to teach the way of God to the ignorant; this is the most valuable, because the most useful gift of the Spirit.
And forbid not to speak with tongues - Let every gift have its own place and operation; let none envy another; nor prevent him from doing that part of the work to which God, by giving the qualification, has evidently called him.

(18) Wherefore, brethren, covet to prophesy, and forbid not to speak with tongues.
(18) Prophecy ought certainly to be retained and kept in congregations, and the gift of tongues is not to be forbidden, but all things must be done orderly.

Wherefore, brethren, covet to prophesy,.... The apostle now draws to a conclusion, and reassumes the exhortation he gave in the beginning of the chapter, pressing the members of this church to desire the gift of prophecy, that being the most eligible and preferable to others, particularly to speaking with tongues, since it was the most useful and edifying, as he abundantly proves:
and forbid not to speak with tongues; such as have that gift, and are desirous of exercising it, provided they observe the rules prescribed, and have an interpreter; this he adds to promote love, and prevent dissension and discord.

covet--earnestly desire. Stronger than "forbid not"; marking how much higher he esteemed "prophecy" than "tongues."

Therefore - To sum up the whole.