prayer vs sacred writing

prayer and sacred writing both are nouns.

Word	Noun	Adjective	Verb	Adverb
prayer	Yes	No	No	No
sacred writing	Yes	No	No	No

As nouns, sacred writing is a hypernym of prayer; that is, sacred writing is a word with a broader meaning than prayer:

Other hypernyms of prayer include religious text, religious writing, sacred text.

prayer (noun)	sacred writing (noun)
the act of communicating with a deity (especially as a petition or in adoration or contrition or thanksgiving)	writing that is venerated for the worship of a deity
earnest or urgent request
a fixed text used in praying
reverent petition to a deity
someone who prays to God