"The day will come when our Republic will be an impossibility because wealth will be concentrated in the hands of a few. When that day comes, we must rely upon the wisdom of the best elements in the country to readjust the laws of the nation." - James MadisonFound at Reddit, where there is discussion and comments re the sources of the quotations.
"Of all the enemies to public liberty war is, perhaps, the most to be dreaded, because it comprises and develops the germ of every other. War is the parent of armies; from these proceed debts and taxes; and armies, and debts, and taxes are the known instruments for bringing the many under the domination of the few. In war, too, the discretionary power of the Executive is extended; its influence in dealing out offices, honors, and emoluments is multiplied; and all the means of seducing the minds, are added to those of subduing the force, of the people. The same malignant aspect in republicanism may be traced in the inequality of fortunes, and the opportunities of fraud, growing out of a state of war, and in the degeneracy of manners and of morals engendered by both. No nation could preserve its freedom in the midst of continual warfare." -James Madison
[the influence of the rich] will have the same effect here as elsewhere if we do not by such a Gov't keep them within their proper sphere. We should remember that the people never act from reason alone. The rich will take advantage of their passions and make these the instruments for oppressing them. The Result of the Contest will be a violent aristocracy, or a more violent despotism. The schemes of the Rich will be favored by the extent of the Country. The people in such distant parts can not communicate & act in concert. They will be the dupes of those who have more Knowledge & intercourse. The only security agst. encroachments will be a select & sagacious body of men, instituted to watch agst. them on all sides. -Gouveneur Morris