"Again, men say that instead of engaging in controversy in the Church, we ought to pray to God for a revival; instead of polemics, we ought to have evangelism. Well, what kind of revival do you think that will be? What sort of evangelism is it that is indifferent to the question what evangel is it that is to be preached? Not a revival in the New Testament sense, not the evangelism that Paul meant when he said, 'Woe is be unto me, if I preach not the gospel.' No, my friends, there can be no true evangelism which makes common cause with the enemies of the Cross of Christ. Souls will hardly be saved unless the evangelists can say with Paul: "If we or an angel from heaven preach any other gospel than that which we preached unto you, let him be accursed!"
Every true revival is born in controversy, and leads to more controversy. That has been true ever since our Lord said that He came not to bring peace upon the earth but a sword. And do you know what I think will happen when God sends a new Reformation upon the Church? We cannot tell when that blessed day will come. But when the blessed day does come, I think we can say at least one result that it will bring. We shall hear nothing on that day about the evils of controversy in the Church. All that will be swept away as with a mighty flood. A man who is on fire with a message never talks in that wretched, feeble way, but proclaims the truth joyously and fearlessly, in the presence of every high thing that is lifted up against the gospel of Christ."
J. Gresham Machen, The Importance of Christian Scholarship, p.10, pdf.