George Washington Letter on God and the Constitution Revealed

L - An engraving by C. Burt featuring George Washington, the 1st President of the United States. R - a fragment of a rare letter written by George Washington that has come for auction, according to The Raab Collection, a dealer in historical documents. Hulton Archive/Getty Images; The Raab Collection

A unique letter written by George Washington that makes reference to God and the Constitution is up for sale after spending decades in a private collection.

The remarkable piece of correspondence is expected to fetch in excess of $100,000.