3,885. The Holiest Location of Them All

Hilchos Beis HaBechirah 7:21

The Heichal is holier than the preceding area; only kohanim who have sanctified their hands and feet may enter.

Hilchos Beis HaBechirah 7:22

The Holy of Holies is holier still. Only the Kohein Gadol may enter there, when performing the service on Yom Kippur.