James Madison wrote this in his Detached Memoranda on the First Amendment:

Let (the American People) exert the same wisdom, in watching against every evil lurking under plausible disguises, and growing up from small beginnings.

This is the same document in which he wrote that

Strongly guarded as is the separation between Religion & Govt in the Constitution of the United States the danger of encroachment by Ecclesiastical Bodies, may be illustrated by precedents already furnished in their short history…

Madison is the Founder known as the Father of the Constitution. He wrote the Memoranda around 1817-1820.