For the Puritans, and the Westminster Assembly especially, preaching was only right preaching when the text was central; for the responsible preacher, the Scripture passage was to guide the sermon, not allowing his sermon to mold the Scripture or to go beyond what the text was saying.
The Puritan movement was known firstly as a resurgence of biblical of preaching; its focus was upon the right preaching of God’s word which would transform and revive not only the Church but also the nation, and if the Lord so willed, also the world! As Dr. Irvonwy Morgan understood it, “the essential thing in understanding the Puritans was that they were preachers before they were anything else…. Into whatever efforts they were led in their attempts to reform the world through the Church, and however these efforts were frustrated by the leaders of the Church, what bound them together, undergirded their striving, and gave them the dynamic to persist was their consciousness that they were called to preach the Gospel.”
If William Perkins is regarded as the Father of Puritan preaching with his publishing of The Art of Prophesying, a book which planted the seeds of Biblical exposition in the Puritan psyche, then it may also be said that the Westminster Assembly was the flowering of that seed. Indeed, in the Assembly’s outlining of what proper preaching ought to look like, it was to William Perkins where they found their model. The emphasis which both Perkins and the Assembly aimed to establish was that the preaching ought always be centered upon and grounded in the Word.
Hence Perkins claimed, “The Word of God alone is to be preached, in its perfection and inner consistency. Scripture is the exclusive subject of preaching, the only field in which the preacher is to labor.” It was from this that the Westminster Divines wrote that “the subject of [a preacher’s] sermon is to be some text of Scripture… he may go on in some chapter, psalm, or book of the holy Scripture, as he shall see fit.” In fact, they go on to advise that when applying or bringing about any doctrine in their sermons, preachers are to make sure “it be a truth contained in or grounded on that text, that the hearers may discern how God teacheth it from thence… The doctrine is to be expressed in plain terms… it is to be opened, and the consequence also from the text cleared.”