Answer:
The establishment clause.
Step-by-step explanation:
Establishment clause, also called establishment-of-religion clause, clause in the First Amendment to the U.S. Constitution forbidding Congress from establishing a state religion. It prevents the passage of any law that gives preference to or forces belief in any one religion. It is paired with a clause that prohibits limiting the free expression of religion.
As the citizenry became more diverse, however, challenges arose to existing laws and practices, and eventually, the Supreme Court was called upon to determine the meaning of the establishment clause.
Though not explicitly stated in the First Amendment, the clause is often interpreted to mean that the Constitution requires the separation of church and state.