1 Pursue love, and desire spiritual gifts, but especially that you may prophesy.
2 For he who speaks in a tongue does not speak to men but to God, for no one understands him;however, in the spirit he speaks mysteries.
3 But he who prophesies speaks edification and exhortation and comfort to men.
4 He who speaks in a tongue edifies himself, but he who prophesies edifies the church.
5 I wish you all spoke with tongues, but even more that you prophesied; for he who prophesies is greater than he who speaks with tongues, unless indeed he interprets, that the church may receive edification.
6 But now, brethren, if I come to you speaking with tongues, what shall I profit you unless I speak to you either by revelation, by knowledge, by prophesying, or by teaching?
pursue love (v.1) — connected to 1 Corinthians 13:13
The original Greek does not say “an unknown tongue” [as the KJV does]. It says simply, “He that speaketh in a tongue.” The genuine gift of tongues was the supernatural gift of speaking in another language without its having been learned. This verse makes it clear that he who speaks in a tongue, unless the tongue is interpreted, would be speaking “not unto men, but unto God.” The same is true in verse 14 where Paul refers to praying in a tongue. He would edify himself alone unless he interpreted, in which case his interpretation would have the same value as the superior gift of prophesying.
The gift of tongues, though a dangerous gift, was highly coveted in the Corinthian church, and the person who possessed this gift was very likely to develop a certain spiritual pride in such possession. Also, the very desire to possess the gift of tongues could produce a kind of self-hypnotism, a deliberately-induced hysteria which issued forth in a synthetic, completely false and deluded speaking with tongues. — Greene, pages 440-441
in the spirit (v.2) — as opposed to “with understanding” (v.14)
edification (v.3) = building
edifies himself (v.4) — not by increasing his understanding, unless he could also interpret, but through encouragement received from evidence of the Spirit — so, tongues was not to be done in the assembly because, if only the speaker was edified (in the sense of proving he had the Spirit), it was selfish.
I wish you all spoke with tongues (v.5) — keep in mind that this was during the transition period between law and grace when kingdom signs were still given.
Prophesy, in these verses, was a gift whereby God gave people His Word to edify others with — a gift no longer given after the canon was complete.