Thomas Jefferson, in his own words

Christianity neither is, nor ever was a part of the common law. -- letter to Dr. Thomas Cooper, February 10, 1814

Millions of innocent men, women and children, since the introduction of Christianity, have been burnt, tortured, fined and imprisoned; yet we have not advanced one inch towards uniformity. -- Notes on Virginia, 1782

Question with boldness even the existence of a god; because if there be one he must approve of the homage of reason more than that of blindfolded fear. -- Letter to Peter Carr, August 10, 1787

Where the preamble declares, that coercion is a departure from the plan of the holy author of our religion, an amendment was proposed by inserting "Jesus Christ," so that it would read "A departure from the plan of Jesus Christ, the holy author of our religion;" the insertion was rejected by the great majority, in proof that they meant to comprehend, within the mantle of its protection, the Jew and the Gentile, the Christian and Mohammedan, the Hindoo and Infidel of every denomination. -- in reference to the Virginia Act for Religious Freedom

I concur with you strictly in your opinion of the comparative merits of atheism and demonism, and really see nothing but the latter in the being worshipped by many who think themselves Christians. --letter to Richard Price, Jan. 8, 1789

Believing with you that religion is a matter which lies solely between man and his God, that he owes account to none other for his faith or his worship, that the legislative powers of government reach actions only, and not opinions, I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should 'make no law respecting an establishment of religion, or prohibiting the free exercise thereof,' thus building a wall of separation between church and State. --letter to Danbury Baptist Association, CT., Jan. 1, 1802

History, I believe, furnishes no example of a priest-ridden people maintaining a free civil government. This marks the lowest grade of ignorance of which their civil as well as religious leaders will always avail themselves for their own purposes. -- to Alexander von Humboldt, Dec. 6, 1813.

In every country and in every age, the priest has been hostile to liberty. He is always in alliance with the despot, abetting his abuses in return for protection to his own. -- letter to Horatio G. Spafford, March 17, 1814