Even when you include the amendments, the Constitution says only three things about religion. Here’s exactly what the Constitution says about the subject:
Article VI: “No religious rest shall ever be required as a Qualification to any Office or public Trust un the United States.”
Amendment I: “Congress shall make to law respecting an establishment of religion, or prohibiting the free exercise thereof.”
In other words: (1) The government is not allowed to make people take a religious test in order to qualify for holding federal office; (2) Congress is not allowed to set up an official national church; and (3) Congress is not allowed to stop people from practicing their religions.
These three rules are meant to protect your liberty to follow God, not to abolish it. That famous slogan about a “wall of separation” just isn’t there.
— J. Budziszewski, from How to Stay Christian in College, p. 118