From the page: religion is mentioned only twice in the Constitution. The last line of Article Six of the US Constitution says, "...no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States." This is a prohibition against religion clearly stating that religion cannot be a condition of government service.
Religion is mentioned again in the First Clause of the First Amendment of the Constitution, in what is known as the Bill of Rights. The First Amendment requires that "Congress shall make no law respecting an establishment of religion..." It's another prohibition. It is a prohibition that applies only to religion. It means that the government cannot dictate or create an official religion for the United States. Period. Government must be neutral on the subject of religion - it can provide no favoritism based on bronze-age superstitions.