Charles Ellicott Commentary Hebrews 9:3

"And after the second veil, the tabernacle which is called the Holy of holies;" — Hebrews 9:3 (ASV)

The tabernacle.—Rather, a tabernacle which is called the Holy of Holies. This literal translation of a Hebrew expression for “most holy” does not occur in the Bible, but has become familiar through the Latin sanctum sanctorum.

The inner chamber of the Tabernacle is mentioned separately in only a few passages in the Pentateuch as the “Most Holy Place” (Exodus 26:33–34), or “the Holy Place” (Leviticus 16:2, and others).

In the description of the Temple, a different word is employed, always translated as “oracle” (1 Kings 6:16, and others).

The veil separating the two divisions (Exodus 36:35) is here called the second veil, to distinguish it from the “hanging for the door” of the Tabernacle (Exodus 26:36; Exodus 36:37).