“I am certainly not an advocate for frequent and untried changes in laws and constitutions.”

An abridged version is inscribed on the Jefferson Memorial in Washington, D.C., http://www.monticello.org/site/jefferson/quotations-jefferson-memorial as follows:
I am not an advocate for frequent changes in laws and constitutions, but laws and institutions must go hand in hand with the progress of the human mind. As that becomes more developed, more enlightened, as new discoveries are made, new truths discovered and manners and opinions change, with the change of circumstances, institutions must advance also to keep pace with the times. We might as well require a man to wear still the coat which fitted him when a boy as civilized society to remain ever under the regimen of their barbarous ancestors.
1810s, Letter to H. Tompkinson (AKA Samuel Kercheval) (1816)
Context: I am certainly not an advocate for frequent and untried changes in laws and constitutions. I think moderate imperfections had better be borne with; because, when once known, we accommodate ourselves to them, and find practical means of correcting their ill effects. But I know also, that laws and institutions must go hand in hand with the progress of the human mind. As that becomes more developed, more enlightened, as new discoveries are made, new truths disclosed, and manners and opinions change with the change of circumstances, institutions must advance also, and keep pace with the times. We might as well require a man to wear still the coat which fitted him when a boy, as civilized society to remain ever under the regimen of their barbarous ancestors. It is this preposterous idea which has lately deluged Europe in blood. Their monarchs, instead of wisely yielding to the gradual change of circumstances, of favoring progressive accommodation to progressive improvement, have clung to old abuses, entrenched themselves behind steady habits, and obliged their subjects to seek through blood and violence rash and ruinous innovations, which, had they been referred to the peaceful deliberations and collected wisdom of the nation, would have been put into acceptable and salutary forms. Let us follow no such examples, nor weakly believe that one generation is not as capable as another of taking care of itself, and of ordering its own affairs.