Something that is so out of time in religious book (4)
I believe the answer is:
ruth
'book' is the definition.
(book of the Bible)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for ruth that I've seen before include "She is followed by Samuel" , "Girl's name; pity (archaic)" , "Old word for pity, or Bible book" , "Lady" , "condolence" .)