Jonathan Edwards’s purpose in delivering the sermon, "Sinners in the Hands of an Angry God" is to warn his congregation in particular, and presumably, by extension, his nation as a whole, that they must repent of their sinful ways and turn to God for forgiveness before it is too late - so that they can escape death by hell fire.
In essence, Jonathan Edward's is saying that the opportunity is now to embrace and accept Jesus Christ, his message, his teachings, and his sacrifice as atonement for sins. The choice must be made by those God is calling, through Jesus Christ, to either accept the call to repentance and a new life, or reject it.
Rejection will result in death by hell fire. Edwards indicates that God is extending mercy by calling out to sinners - He is giving them an opportunity to accept Jesus' sacrifice and start a new life of obedience to Christ - to become slaves of Christ - subject to his mastery over them. Edwards' purpose with this sermon is to awaken people to the seriousness of their situation because of sin - and that Christ is their only way to true redemption and a real eternal life. Edwards is encouraging his congregation to flee,run, from the wrath that is to come upon the unrepentant and unbelieving. He trumpets the necessity of accepting Christ and his atoning death. This is indicated in the Scriptures as well in this verse:
"that at the name of Jesus every knee should bow, in heaven and on earth and under the earth,"
(Philippians 2:10 - New International Version (NIV) )
The fire and brimstone sermon by Jonathan Edwards is meant to throw fear into the hearts of those wayward Puritans- of his congregation, for as Ralph Waldo Emerson wrote, "Fear is an instructor of great sagacity and the herald of all resolutions." Paradoxically, Edwards was a Calvinist who believed in predestination, yet he also believed people are responsible for their actions. And, so, he preaches a sermon that is replete with fear-inspiring imagery.
The prevailing image of this sermon is the image of the bottomless pit of hell whose fiery floods wax high enough to burn the gossamer thread that holds the unworthy souls who are weighted down with wickedness in the first place. Edwards speaks in hyperbole: "the floods of God's vengeance"; "the fiery floods of fierceness"; the bow of God's wrath is bent, and the arrow made ready on the string and justice bends the arrow at your heart."
This frightening sermon of Edwards is constructed around a passage from Deuteronomy in the Old Testament of the King James Version of the Bible: "The foot shall slide in due time." Using the metaphor of a slippery slide, Edwards, at a revival where his famous sermon was given, points to the dangers of spiritual sliding. The yawning abyss waits for the sinners, whose wickedness makes them "heavy as lead," and only the "mere pleasure" of God keeps them from burning in the images of "fiery floods" and "fire of wrath." Especially, the image of the sinner held over the fires of hell by only a gossamer thread is effectively fear-inspiring as many Puritans fled in fear from Edwards's revival.
The following passages are excerpts from eNotes' study guide for Sinners in the Hands of and Angry God and describe the intended purpose for the sermons of this era.
"This revival movement stirred many to intensify their religious seriousness, not only in Edwards’s own congregation of Northampton but also throughout New England. His sermons were intended as a wake-up call for those who underplayed the majesty of a holy God and overemphasized their own worthiness as decent, hard-working, successful citizens. Edwards believed strongly that only a genuine conversion experience should qualify a person for church membership. Revivalist preachers, therefore, sought not only to address the intellect but also to engage the emotions so as to convince the listeners of the seriousness of their sin and activate them to seek salvation from the punishment they could expect from a righteous God."
However, there was one congregation that did not display a profound change in attitude or emotion. Edwards wrote the sermon "Sinners in the Hands of an Angry God" specifically for this audience.
"The results were encouraging, but one congregation, that in Enfield, Connecticut, seemed to be immune to the call for radical conversion. Edwards was therefore invited to preach there. On July 8, 1741, at the height of the Great Awakening, he delivered a revival sermon in Enfield that became the most famous of its kind. He followed the traditional three-part sermon structure: a scripture text, which is the foundation for the sermon, and an exposition of its implications; discussion of the doctrine that is derived from the text; and the application of the doctrine to the personal situation of the listeners. Edwards carefully selected the text for this occasion, for it was his single-minded intent to disturb profoundly the comfortable members of his audience."