"Their foot shall slip in due time." (Deuteronomy 32:35)
In this verse is threatened the vengeance of God on the wicked unbelieving Israelites, who were God's visible people, and who lived under the means of grace; but who, notwithstanding all God's wonderful works towards them, remained void of counsel, having no understanding in them. Under all the cultivations of heaven, they brought forth bitter and poisonous fruit.
Edwards then maps out several ways in which sinners will eventually be punished, even when it appears that they are not.
That the reason why they are not fallen already and do not fall now is only that God's appointed time is not come. For it is said, that when that due time, or appointed time comes, their foot shall slide. Then they shall be left to fall, as they are inclined by their own weight. God will not hold them up in these slippery places any longer, but will let them go; and then, at that very instant, they shall fall into destruction...
The sermon is notorious for its fire and brimstone image of religion. It concludes with a warning:
And let every one that is yet out of Christ, and hanging over the pit of hell, whether they be old men and women, or middle aged, or young people, or little children, now hearken to the loud calls of God's word and providence. This acceptable year of the Lord, a day of such great favour to some, will doubtless be a day of as remarkable vengeance to others. Men's hearts harden, and their guilt increases apace at such a day as this, if they neglect their souls; and never was there so great danger of such persons being given up to hardness of heart and blindness of mind. God seems now to be hastily gathering in his elect in all parts of the land; and probably the greater part of adult persons that ever shall be saved, will be brought in now in a little time... and the rest will be blinded. If this should be the case with you, you will eternally curse this day, and will curse the day that ever you was born, to see such a season of the pouring out of God's Spirit, and will wish that you had died and gone to hell before you had seen it...
Therefore, let every one that is out of Christ, now awake and fly from the wrath to come. The wrath of Almighty God is now undoubtedly hanging over a great part of this congregation. Let every one fly out of Sodom: "Haste and escape for your lives, look not behind you, escape to the mountain, lest you be consumed."