While googling about whether "atheist" should be capitalized, and skimming past posts by people blogging about atheism rather than about English grammar, I came across http://uwf.edu/writelab/reviews/capitalization/
[Capitalize] Religions and religious terms
Catholicism, Hinduism, Buddha, the Bible, Christian, the Ten Commandments, Baptist church, Mt. Zion Methodist Church
NOTE: Do not capitalize the following:
church, communion, atheist, agnostic, spirituality
but I don't recall hearing of such a prescription before. Wouldn't most of the examples listed be capitalized because they're proper nouns? Are there good examples of words being capitalized solely because they're religious terms?
I'm mainly interested in modern English, rather than days of past where a lot more words were capitalized than they are nowadays.
Somewhat related: When should the word "God" be capitalized? - use "God" when referring to the name of the god of Judaism and Christianity (a proper noun), but "god" when referring to the general concept of a deity (common noun).