Thomas Jefferson's letter to the Danbury Baptist in which the words, "Separation of Church and State" first appear.

http://www.free2pray.info/Danbury.html

Jefferson & Separation of Church and State Getting Involved

To Messrs. Nehemiah Dodge and Others, a Committee of the Danbury Baptist Association, in the State of Connecticut Gentleman, The affectionate sentiments of esteem and approbation which you are so good as to express towards me, on behalf of the Danbury Baptist Association, give me the highest satisfaction. My duties dictate a faithful and zealous pursuit of the interests of my constituents, and in proportion as they are persuaded of my fidelity to those duties, the discharge of them becomes more and more pleasing. 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. Adhering to this expression of the supreme will of the nation in behalf of the rights of conscience, I shall see with sincere satisfaction the progress of those sentiments which tend to restore to man all his natural rights, convinced he has no natural right in opposition to his social duties.  I reciprocate your kind prayers for the protection and blessing of the common Father and Creator of man, and tender you for yourselves and your religious association, assurances of my high respect and esteem. Th. Jefferson January 1, 1802