Natural Right
The framers [of The United States Constitution] generally held that religious free exercise is a natural right that belongs to all individuals.
Article II of Delaware’s 1776 Declaration of Rights, for example, states “that all men have a natural and unalienable right to worship Almighty God according to the dictates of their own consciences and under-standings . . . .” (Kurland and Lerner 2001, 5:70). The same or similar natural rights language can be found in several of the early state constitutions – including Pennsylvania (1776), North Carolina (1776), and New Hampshire (1784) (Poore 1878, 1541, 1410, 1281) – and other significant founding-era documents. George Washington’s ([1790] 1988, 548) letter to the Hebrew Congregation at Newport, Rhode Island, captures the founders’ common understanding. “All possess alike liberty of conscience and immunities of citizenship,” Washington writes. He then continues:
“It is now no more that toleration is spoken of as if it were the indulgence of one class of people that another enjoyed the exercise of their inherent natural rights, for, happily, the Government of the United States, which gives to bigotry no sanction, to persecution no assistance, requires only that they who live under its protection should demean themselves as good citizens in giving it on all occasions their effectual support.”
By “inherent,” Washington means that the right of religious liberty inheres in the individual absent of, and prior to, any state recognition or state action. As a natural right, religious liberty is not understood to be created by the state or by the mutual consent of citizens. Rather, the founders locate religious liberty in man’s created nature and his prepolitical obligations to his creator.
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2796598
Article VI, Clause 3 (1788)
No Religious Test Clause:
The Constitution of the United States provides that “no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States.” During the ratification debates, a framer of the Constitution explained that this clause prohibits examination of “one’s belief of certain doctrines…for the purpose of determining whether his religious opinions are such, that he is admissible to a publick office.”
https://www.religiousfreedominstitute.org/blog/cornerstone-forum-the-no-religious-test-clause-today
1st amendment (1791)
The establishment clause, the free exercise clause:
The First Amendment contains two religion “clauses” – the ban on establishment of religion, and the guarantee of the “free exercise” of religion. The two clauses were intended by the founders to achieve a single overriding purpose: free exercise equality. Their goal was to protect the right of religious free exercise for all Americans, and all of America’s religious communities, against the power of government.
…Justice Thomas noted that the Establishment Clause was designed to prevent government coercion of religion, which typically occurred through attempts “to control religious doctrine or personnel, compel religious observance, single out a particular religious denomination for exclusive state subsidization, or punish dissenting worship.”
“Congress shall make no law … prohibiting the free exercise (of religion)” is called the free-exercise clause of the First Amendment. The free-exercise clause pertains to the right to freely exercise one’s religion. It states that the government shall make no law prohibiting the free exercise of religion.
Although the text is absolute, the courts place some limits on the exercise of religion…. The Supreme Court has interpreted this clause so that the freedom to believe is absolute, but the ability to act on those beliefs is not.
14th Amendment (1868)
The 14th Amendment to the U.S. Constitution, ratified in 1868, granted citizenship to all persons born or naturalized in the United States… and guaranteed all citizens “equal protection of the laws.”
https://www.history.com/topics/black-history/fourteenth-amendment
The 14th Amendment did not universally apply to freedom of religion until Cantwell v. Connecticut, 310 U.S. 296 (1940).
Cantwell v. Connecticut, 310 U.S. 296 (1940)
Cantwell v. Connecticut, 310 U.S. 296 (1940) stands as the first case in which the Supreme Court applied First Amendment freedom of religion rights to the states via the due process clause of the Fourteenth Amendment.
https://www.mtsu.edu/first-amendment/article/273/cantwell-v-connecticut