holy of holies

nouns

(figurative) something regarded as sacred or inviolable
"every politician fears to touch that holy of holies, the Social Security System"
holy of holies
is a type of (narrower)
the quality of being sacred
sacredness
(Judaism) sanctuary comprised of the innermost chamber of the Tabernacle in the temple of Solomon where the Ark of the Covenant was kept
holy of holies, sanctum sanctorum