Though Bunyan's first appearance as an author was in the region of controversy, it was not along this line his best work was to be done. He was to win the homage of men's hearts by holding up those central verities on which Christians are mainly agreed, and by unfolding the fairer aspects of that life from God which makes them one. Preaching became the passion, as it had become the work, of his life. He gave himself wholly to it, in the sense that he was a whole man in it. At a later time, as he lay a prisoner in Bedford Gaol, he went back in thought over the five years between 1655 and 1660, when he was at large, and laid bare for us the heart-experiences to which he was no stranger as he pleaded with men. More than most, he compassed the range, ascended the heights, and sounded the depths of the preacher's life. Sometimes, he says, he would start with clearness, evidence, and liberty of speech, and before long become so straitened before the people that it seemed to him as if his "head had been in a bag all the time of the exercise." Sometimes he would be seized with a strange faintness and strengthlessness of body on his way to the place of meeting, and afterwards be "tempted to pride and liftings up of heart" at his hold over the people. With the instinct of a real prophet of God, he wished to see the truth, not through other men's eyes, but through his own. He could not use other men's lines, finding "by experience that what was taught him by the Word and Spirit of Christ could be spoken to, maintained, and stood to by the soundest and best established conscience." No preacher of doubts was he, but of assured verities. He felt, he says, "as if an Angel were at his back"; that which he spoke lay with such power and heavenly evidence upon his soul that he could "not be contented with saying I believe and am sure; he thought I was more than sure (if it be lawful so to express myself) that those things which then I asserted were true."
With the true preacher's passionate longing, he strove to get firm grip of the souls of his hearers. "In my preaching I have really been in pain, I have, as it were, travailed to bring forth Children to God." If his work were fruitless it mattered little who praised, or if it were fruitful, who condemned. He often noticed that "when he had a work to do for God in a place, there was a great going of God upon his spirit, leading him to desire to go there." He also observed that such and such souls in particular were strongly set upon his heart, and these very souls afterwards given him as the fruits of his ministry. It was not always his best preparation he found to be most effective. "A word cast in by the by hath done more execution in a Sermon than all that was spoken besides." Sometimes, when he thought he had done no good he did most, and at other times, when he thought he should catch men, he . . . fished for nothing. Occasionally he has been about to take up some smart and searching portion of the word, when up starts the Tempter and asks him if he really is going to preach a Truth which so plainly condemns himself; but he thanks God, who helped him to put down these horrid suggestions, and to bow himself with all his might to condemn Sin and Transgression wherever found, even upon his own conscience. "Let me die, thought I, with the Philistines, rather than deal corruptly with the blessed Word of God."
When tempted to vanity over his success, "the Lord of his precious mercy hath so carried it towards me that for the most part I have but small joy to give way to such a thing. For it hath been my every day's portion to be let into the evil of my own heart, and still made to see such a multitude of corruptions and infirmities therein that it hath caused hanging down of the head under all my Gifts and Attainments. I have felt this thorn in the Flesh the very God of mercy to me." He saw that, if he had gifts, but wanted saving grace, he was but as a tinkling cymbal. "This consideration was as a maul on the head of Pride and desire of vain glory. What, thought I, shall I be proud because I am a sounding brass? Is it so much to be a Fiddle?" Love will never die, but gifts will cease and vanish; gifts are not our own, but the Church's, and to be accounted for in stewardship. Gifts, indeed, are desirable, but yet great grace and small gifts are better than great gifts and no grace. At sight of this the snare was broken and he escaped. The enemy not being able to overthrow him by inward temptations set about outward opposition. Bunyan noticed, and could "instance particulars" to show, that "where the Lord was most at work Satan was busiest, hath there begun to roar in the hearts, and by the mouths of his servants; where the world has raged most there souls have been most awakened."