What document contains the phrase "Separation of church and state"?

yeah I bet lots of people thought that this was part of the Constitution... I even hear dumb politicians say it....the Constitution forbids the formation of a state sponsored religion...no where is the so called seperation clause found.... just used by the heathen polititions to get God out of our lives... what a shame.

I knew that Jefferson wrote a few letters like this but this one sounded like one of the Bill of rifhts