If you have been preaching for any length of time you know the experience. You are deep into the sermon when some fresh idea comes unbidden to your mind. It seems to be a worthy idea, but then you don’t exactly have time to give it full consideration, given that you are preaching in full flight. Do you use it?
Whether or not you use an unconsidered insight will depend upon things like your risk tolerance, your sense of discipline, and your Spirit-guided instinct. Great preachers have good instincts, guided by the Holy Spirit and developed over a long period of discipleship. The more we know the Word and the better we know our Lord, the better we can trust ourselves to think on our feet.
Some will say that one should never give one’s self such license – that the only things worth saying are the things that have been carefully and prayerfully considered. It is good advice, except for the fact that it doesn’t fully appreciate what is happening in preaching. Preaching is a corporate dialogue with God by his Spirit through his Word. It happens in the community of God as we collectively try to listen to his voice. When practiced at its best, there is a vitality in preaching that comes from knowing that this is an event in God’s presence that is unique and unrepeatable. Great preachers are alive to what God is doing in the moment, listening for the Spirit, tracking with the crowd and giving voice to the Word. It cannot possibly be fully planned in advance.
To say that good preachers have good instincts does not mean that they have a special freedom to make the sermon up in the moment of its preaching. That would be irresponsible. It does mean, however, that the preacher has walked with God for a long time, is present to God through prayer, and has honed the discipline of recognizing truth from error. This is one of the reasone that preaching is not a work for spiritual novices.
Great preachers have great instincts. Those instincts, like every other aspect of their lives, have been brought under the Lordship of Christ and are offered in the service of his people.