Well, the Constitution talks about religion in two places:
1. “No religious test shall ever be required as a qualification to any office or public trust” (Art. VI)
2. “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof” (First Amendment).
Thanks to the founders, we have a secular government. But the majority of the citizens are Christian.
Those who use the religious test as a sign of a secular government are ignoring the context in which it was written. The point was to avoid preferences to specific denominations or a state church (remember that when Article VI was written there was no 1st Amendment yet) not to make the government completely secular. Electing an atheist or (if they had been present) a Hindu or Muslim to office would have been as bizarre an idea to the people of 18th Century America as the idea of electing the President of NAMBLA to the Senate is to us, so they didn’t need to spell that out.
Plus, there’s a great difference between a completely secular government and a theocracatic government, but too many people seem to believe that we have one or the other, not a nation established as Christian and structured to be tolerant. For example, the deist president of a secular nation would not have transferred money to missionaries out of the treasury, and there would not be numerous Founder quotes discussing the need for religion and morality in the governing process.
Well no, there's one more. You missed the one where it specifically refers to the little baby Jesus.