"廁內平安"?!

I noticed that there are several people using 廁內平安 as their 參考資料 when posting an answer in the Christianity category.

What is 廁內平安? Is it the title of a book? Who is the author? The publisher? ISBN#? Written in which year?

Since it is a reference, surely I can refer to that as well. I am really interested in what is that about.