Speaking in tongues should be for edifying the church
The most important word which characterises the chapter about the gift of Speaking in tongues (1Cor.14), is the word edifying. The Apostle mentions it many times and emphasises it. He says explicitly: “Let all things be done for edification” (1Cor.14: 26) and “Even so you, since you are zealous for spiritual gifts, let it be for the edification of the church that you seek to excel” (1Cor.14: 12).
For the sake of edifying the church, the Apostle says that "he who prophesies is greater than he who speaks with tongues” (v.5) because “he who speaks in a tongue edifies himself, but he who prophesies edifies the church” (v.4). The word prophesy at that time also meant teaching. The Apostle prefers prophesying because “he who prophesies speaks edification and exhortation and comfort to men” (v.3).