1 Cor. 14:1-5 (ESV)
Pursue love, and earnestly desire the spiritual gifts, especially that you may prophesy.  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.  On the other hand, the one who prophesies speaks to people for their upbuilding and encouragement and consolation.  The one who speaks in a tongue builds up himself, but the one who prophesies builds up the church.  Now I want you all to speak in tongues, but even more to prophesy. The one who prophesies is greater than the one who speaks in tongues, unless someone interprets, so that the church may be built up.
What does it mean to prophesy? The Bible uses this word in a couple different ways. In the Old, and in the New Testament for a time, it was used to mean the utterance of what we would call special and direct revelation from God. In the absence of God’s written word this was needed in the New Testament also. It was kept in check by the Apostles. One reason Paul wrote to the Corinthians, was no doubt the effect of false prophecies given to the Corinthian church. Today we have God’s word, we can test the spirits by it, and we have no reason for special revelation. But there is another sense in which prophecy still exists and this is speaking the Word of God in such away as to build people up, encourage them, and console them. This is a special gift. One we should all earnestly desire. Upbuilding, encouragement, and consolation, are the effects of the Gospel, the forgiveness of sins. It isn’t always easy to get people to trust that, or to even point them to it. There are many who are ruined by false prophets, those who, wittingly or unwittingly, abuse the scriptures in applying them to people. They only give them law. They don’t give them the gospel. In this way the build up their sinful pride, or they drive them to despair. We can’t give the gospel without the law. The law has to work, it has to bring one to despair. But then the gospel becomes so much sweeter, it build up a persons confidence in Christ. It encourages them to believe. And it consoles them. This the law cannot do.