“. . . Because finally, ‘the equal right of every citizen to the free exercise of his Religion according to the dictates of conscience’ is held by the same tenure with all our other rights. If we recur to [go to] its origin, it is equally the gift of nature; . . .”

The belief expressed in the above statement was put into law by
a. signing of the Mayflower Compact
b. creation of the Articles of Confederation
c. establishment of a federal system of government
d. addition of the first amendment to the United States Constitution

The quoted section in the question comes from a document written by James Madison, titled, Memorial and Remonstrance against Religious Assessments. Madison presented the document to the Virginia Assembly in 1785 as an argument for full religious freedom. It was an argument that found its way also into the Bill of Rights of the US Constitution, specifically in the First Amendment.

The First Amendment states:

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.