Jefferson's interpretation of the first amendment in a letter to the Danbury Baptist Association (January 1, 1802):

"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."

As Thomas Jefferson wrote in his Autobiography, in reference to the Virginia Act for Religious Freedom:

“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"

and James Madison, whom many refer to as the father of the Constitution, also held similar views which he expressed in his letter to Edward Livingston, 10 July 1822:

“And I have no doubt that every new example will succeed, as every past one has done, in shewing that religion & Govt will both exist in greater purity, the less they are mixed together.”