The innermost room of the tabernacle and of the temple, where the ark of the covenant was kept; also called the Holy of Holies. According to the Mosaic Law, the only person allowed to enter the Most Holy was the high priest, and he could enter only on the annual Day of Atonement.​—Ex 26:33; Le 16:2, 17; 1Ki 6:16; Heb 9:3.