1 Corinthians 14:2-4

When someone speaks in tongues, no one understands a word he says, because he’s not speaking to people, but to God—he is speaking intimate mysteries in the Spirit. But when someone prophesies, he speaks to encourage people, to build them up, and to bring them comfort. The one who speaks in tongues advances his own spiritual progress, while the one who prophesies builds up the church.