3,979. The Kodesh and the Kodesh HaKodashim

Hilchos Bias HaMikdash 2:1

The Kohein Gadol enters the Kodesh HaKodashim (the Holy of Holies) only one day per year – Yom Kippur. A regular kohein may enter the Kodesh (the Sanctuary) every day to serve.

Hilchos Bias HaMikdash 2:2

All kohanim were warned not to enter the Kodesh or the Kodesh HaKodashim other than at the time of the service. This is as per Leviticus 16:2: “He shall not come to the holy at all times.” This refers to the Kodesh HaKodashim; the words “within the curtain” come to include the rest of the Temple.