Sermon: From the Latin, "discourse, conversation"

"For many centuries, from the early Middle Ages onward, sermons reached a far larger audience than any other type of non-ritualistic discourse, whether oral or written. They are entirely in the oral tradition, of course, with the sermonist as the speaker and the congregation as the hearers, and with a live relation between the two. The sermon gains in potential effect because of the hallowed nature of the occasion and the religious nature of the message. Moreover, the speaker is a figure endowed with special authority and set apart from the willing hearers who are listening."
(James Thorpe, The Sense of Style: Reading English Prose. Archon, 1987)

"I have been rather reluctant to have a volume of sermons printed. My misgivings have grown out of the fact that a sermon is not an essay to be read but a discourse to be heard. It should be a convincing appeal to a listening congregation."
(Martin Luther King, Jr. Preface to Strength to Love. Harper & Row, 1963)

"The various means through which hearers are gratified implies, of course, that a sermon may answer to very different needs. . . . In a sense, these motives for audience attendance correspond with the threefold aim of classical rhetoric: docere, to teach or persuade the intellect; delectare, to delight the mind; and movere, to touch the emotions."
(Joris van Eijnatten, "Getting the Message: Toward a Cultural History of the Sermon." Preaching, Sermon and Cultural Change in the Long Eighteenth Century, ed. by J. van Eijnatten. Brill, 2009)

St. Augustine on the Rhetoric of the Sermon
"After all, the universal task of eloquence, in whichever of these three styles, is to speak in a way that is geared to persuasion. The aim, what you intend, is to persuade by speaking. In any of these three styles, indeed, the eloquent man speaks in a way that is geared to persuasion, but if he doesn’t actually persuade, he doesn’t achieve the aim of eloquence."
(St. Augustine, De Doctrina Christiana, 427, trans. by Edmund Hill)

"It was perhaps inevitable that Augustine's opinion would have a strong influence on the future development of rhetoric . . .. Moreover, the De doctrina provides one of the few basic statements of a Christian homiletic prior to the emergence of the highly formalized 'thematic' or 'university style' of sermon about the beginning of the 13th century."
(James Jerome Murphy, Rhetoric in the Middle Ages: A History of Rhetorical Theory From Saint Augustine to the Renaissance. Univ. of California Press, 1974)

Excerpt From the Most Famous American Sermon
"There is no want of power in God to cast wicked men into hell at any moment. Men's hands can't be strong when God rises up: the strongest have no power to resist him, nor can any deliver out of his hands.

"He is not only able to cast wicked men into hell, but he can most easily do it. Sometimes an earthly prince meets with a great deal of difficulty to subdue a rebel that has found means to fortify himself, and has made himself strong by the number of his followers. But it is not so with God. There is no fortress that is any defence against the power of God. Though hand join in hand, and vast multitudes of God's enemies combine and associate themselves, they are easily broken in pieces: they are as great heaps of light chaff before the whirlwind; or large quantities of dry stubble before devouring flames. We find it easy to tread on and crush a worm that we see crawling on the earth; so 'tis easy for us to cut or singe a slender thread that any thing hangs by; thus easy is it for God, when he pleases, to cast his enemies down to hell. What are we, that we should think to stand before him, at whose rebuke the earth trembles, and before whom the rocks are thrown down!"
(Jonathan Edwards, "Sinners in the Hands of an Angry God," delivered at Enfield, Connecticut on July 8, 1741)