Why does Paul stress prophesying instead of tongues speaking? First, Paul says that speaking in tongues is speaking to God but not to people in the church. But prophesying speaks to people in the church, for their edification. Paul wrote,
2 For one who speaks in a tongue speaks not to men but to God; for no one understands him, but he utters mysteries in the Spirit. 3 On the other hand, the one who prophesies speaks to people for their upbuilding and encouragement and consolation. (1 Cor. 14:2-3)
Second, tongues builds up the tongues-speaker only, but prophecy builds up the church. “The one who speaks in a tongue builds up himself, but the one who prophesies builds up the church” (1 Cor. 14:4).
Third, the prophet is greater than the tongues speaker. “The one who prophesies is greater than the one who speaks in tongues, unless someone interprets, so that the church may be built up” (1 Cor. 14:5). Why does Paul stress that concept of “building up the church” again and again? Why does Paul allow for tongues with interpretation only? We go back to that one fundamental purpose of spiritual gifts—for the common good, for the edification of the church, for the spiritual growth of the church.