Holy Of Holies (Noun)

(figurative) something regarded as sacred or inviolable; "every politician fears to touch that holy of holies, the Social Security System".

Nouns denoting attributes of people and objects.

Their commitment to their craft is the holy of holies that guides their every decision.
To challenge the long-standing tradition was to violate the holy of holies of their community.
Freedom of the press is the holy of holies in a democratic society and should be protected at all costs.
Their family legacy is the holy of holies that they will fiercely defend against any criticism or aspersion.
The constitution is the holy of holies that cannot be altered or compromised under any circumstance.

(Judaism) sanctuary comprised of the innermost chamber of the Tabernacle in the temple of Solomon where the Ark of the Covenant was kept.

Nouns denoting man-made objects.

The priest entered the holy of holies once a year to offer sacrifices to atone for the sins of the people.
In the holy of holies, the Ark of the Covenant was placed on a pedestal of gold, symbolizing the presence of God.
Only the high priest could enter the holy of holies, and only on the Day of Atonement, after rigorous purification rituals.
The holy of holies was a cube-shaped chamber, about 15 feet on each side, surrounded by a thick curtain that separated it from the rest of the temple.
The location of the holy of holies in the temple was carefully designed to mirror the arrangement of the heavenly throne room, emphasizing its connection to the divine.