Holy Writ vs religious writing

Holy Writ and religious writing both are nouns.

Word	Noun	Adjective	Verb	Adverb
Holy Writ	Yes	No	No	No
religious writing	Yes	No	No	No

As nouns, religious writing is a hypernym of Holy Writ; that is, religious writing is a word with a broader meaning than Holy Writ:

Other hypernyms of Holy Writ include religious text, sacred text, sacred writing.

Holy Writ (noun)	religious writing (noun)
the sacred writings of the Christian religions	writing that is venerated for the worship of a deity