where is the separation of church and state codified

The separation of church and state is not codified in those exact words in the U.S. Constitution; it is mainly derived from the First Amendment’s Establishment Clause, which says, “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof.”

Where it comes from

• U.S. Constitution, First Amendment : this is the primary legal source.

• Supreme Court interpretation : the doctrine was later developed through court decisions, especially Everson v. Board of Education (1947).

• Jefferson’s phrase : “wall of separation between Church and State” comes from a letter by Thomas Jefferson, not the Constitution itself.

In plain terms

The government cannot establish an official religion or favor one faith over another, and it also cannot interfere with people’s free exercise of religion.

Bottom line

So, if you’re asking where it’s “codified,” the best answer is: in the First Amendment, especially the Establishment Clause, as interpreted by the courts.