“The Jews work more effectively against us than the enemy's armies. They are a hundred times more dangerous to our liberties and the great cause we are engaged in. It is much to be lamented that each state, long ago, has not hunted them down as pests to society and the greatest enemies we have to the happiness of America.”

Sometimes rendered : "They (the Jews) work more effectively against us, than the enemy's armies. They are a hundred times more dangerous to our liberties and the great cause we are engaged in... It is much to be lamented that each state, long ago, has not hunted them down as pest to society and the greatest enemies we have to the happiness of America."
Both of these are doctored statements that have been widely disseminated as genuine on many anti-semitic websites; They are distortions derived from a statement that was attributed to Washington in Maxims of George Washington about currency speculators during the Revolutionary war, not about Jews: "This tribe of black gentry work more effectually against us, than the enemy's arms. They are a hundred times more dangerous to our liberties, and the great cause we are engaged in. It is much to be lamented that each State, long ere this, has not hunted them down as pests to society, and the greatest enemies we have to the happiness of America." More information is available at Snopes. com: "To Bigotry, No Sanction" http://www.snopes.com/quotes/thejews.htm
This quotation is a classic anti-semitic hoax, evidently begun during or just before World War Two by American Nazi sympathizers, and since then has been repeated, for example, in foreign propaganda directed at Americans. In fact it is knitted from two separate letters by Washington, in reverse chronology, neither of them mentioning Jews. The first part of this forgery are taken from Washington's letter to Edmund Pendleton, Nov. 1, 1779 {and the original can be found in the Library of Congress's online service at http://memory.loc.gov/mss/mgw/mgw3h/001/378378.jpg }. I have tried to reproduce Washington's spelling and punctuation exactly. In that letter Washington complains about black marketeers and others undermining the purchasing power of colonial currency:
: … but I am under no apprehension of a capital injury from ay other source than that of the continual depreciation of our Money. This indeed is truly alarming, and of so serious a nature that every other effort is in vain unless something can be done to restore its credit. .... Where this has been the policy (in Connecticut for instance) the prices of every article have fallen and the money consequently is in demand; but in the other States you can scarce get a single thing for it, and yet it is with-held from the public by speculators, while every thing that can be useful to the public is engrossed by this tribe of black gentry, who work more effectually against us that the enemys Arms; and are a hundd. times more dangerous to our liberties and the great cause we are engaged in.
The second part of this fabricated quote is from Washington's letter to Joseph Reed, Dec. 12, 1778 {and can be found at the Library of Congress using the same URL but ending in /193192.jpg}, which again condemns war profiteers (the parenthetical list in the quotation is Washington's own words which he put there in parentheses):
: It gives me very sincere pleasure to find that there is likely to be a coalition … so well disposed to second your endeavours in bringing those murderers of our cause (the monopolizers, forestallers, and engrossers) to condign punishment. It is much to be lamented that each State long ere this has not hunted them down as the pests of society, and the greatest Enemys we have to the happiness of America. I would to God that one of the most attrocious of each State was hung in Gibbets upons a gallows five times as high as the one prepared by Haman. No punishment in my opinion is too great for the Man who can build his greatness upon his Country's ruin.
Misattributed, Spurious attributions