NOTES for Rom 15:14-21
When speaking of his apostolic ministry, Paul does not accidentally emphasize that he never preached where there were already churches founded thanks to the preaching of other witnesses of the Kingdom (vv. 20-21). Evidently, for Paul himself such ministry was a sign that he was bearing witness precisely to Christ and to the Kingdom, and not to his own religion.
Indeed, preaching to those who had already been converted could easily have turned into the preaching of particular ideas and views, all the more when the person involved was as striking in every respect as Paul was. He had plenty to tell besides Christ and the Kingdom. But that would have been possible only if he had preached to those who had already accepted Christ. In that case the apostle really could have begun, as other preachers did, to set out his own views and concepts. But this was exactly what Paul tried with all his strength to avoid, although it is perfectly clear that, had the matter come to concepts, he could have set them out for his listeners in such abundance as no one else could have offered them.
Paul is extremely cautious about instruction and exhortation. He does not seek to become either a teacher or a spiritual guide for those who, as he is convinced, need nothing of the sort (vv. 14-16). He merely reminds the members of the Roman church, as brothers, of what seemed to him fundamentally important for spiritual life.
But evidently this attitude toward his own ministry was important for Paul in another respect as well. He clearly knew how powerful the effect of his witness was and how significant his word was for Christians. Under such circumstances, the mere appearance of the apostle could well have introduced a certain discord into the settled life of a church, where, of course, there were already teachers, guides, and preachers of its own. A person of such stature would inevitably have drawn every eye and all attention to himself in any church, and Paul plainly did not want this at all: for the Kingdom and for witness, such a state of affairs would not have been useful in any way. And the apostle prefers to act where the circumstances themselves will limit his witness exclusively to the theme of Christ and the Kingdom, and where he will in no way be able, even unintentionally, to disturb the life of already existing churches. Just as an apostle should.