A.T. Robertson Commentary Hebrews 9:3

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

After the second veil (μετα το δευτερον καταπετασμα). The first veil opened from outside into the Holy Place, the second veil opened from the Holy Place into the Holy of Holies (Hαγια Hαγιων). The word καταπετασμα is from καταπεταννυμ, to spread down, and we have already had it in 6:19. Cf. also Mt 27:51.