Three issues are at stake here. First, the preacher must be accurate. Paul contrasts this with inaccurate teachers, whose vile mouthings gnaw away like gangrene. Too many are content to offer their congregations predigested information with little thought as to its Biblical accuracy. Others ignore the process altogether and try to attack the enemy with shotguns full of powder but empty of pellets, thinking to bluff with bombast and bluster.
Scripture leaves the preacher with no such alternatives.
He is to be faithful and precise in his understanding and presentation of truth. Second, the preacher should be consistent. It does not matter what aspect of revealed truth is considered, because all truth is of God. Of course, any concept of revelation presupposes the existence of God. The very concept of revelation presupposes the existence of a personal, sovereign God.