It was clearly Paul’s teaching that everyone should participate with the manifestation of the Spirit in the context of the meeting (1 Corinthians 12:7-11, 14:1, 24, 26, 31). He was driving the point home by saying that everyone should prophesy one by one so that the impact would be felt on the unbeliever (1 Corinthians 14:24-25). It is a sign for unbelievers, but is exercised and uttered by believers.