This is a somewhat-paraphrased version of the following:

"...those who live by mystery & charlatanerie, fearing you would render them useless by simplifying the Christian philosophy, the most sublime & benevolent, but most perverted system that ever shone on man, endeavored to crush your well earnt, & well deserved fame." - Thomas Jefferson to Joseph Priestley, Washington, March 21, 1801[1]

Further Sources

• Adams, Dickinson W. (ed.). Jefferson's Extracts from the Gospels: "The Philosophy of Jesus" and "The Life and Morals of Jesus." Princeton: Princeton University Press, 1983.  The introduction to this book has an excellent discussion of Jefferson's thinking on religion.

Footnotes

• 1. PTJ, 33:393. Press copy available from the Library of Congress. Ford transcription available online.