Isaiah 22:22
And the key of the house of David will I lay upon his shoulder; so he shall open, and none shall shut; and he shall shut, and none shall open. And the key of the house of David will I lay upon his shoulder; so he shall open, and none shall shut; and he shall shut, and none shall open.
The key of the house of David placed upon the shoulder signifies that Jesus possesses sovereign authority to open and to shut doors in a manner that no other power can overturn. What he opens remains open despite all opposition, and what he shuts remains shut despite all efforts to reopen it. This authority governs access to the apartments of the heavenly sanctuary and determines where his mediatorial work is carried forward.
In 1844, having completed his mediation in the Holy Place, he closed the door of that apartment and opened the door into the Most Holy Place. Within that inner apartment stands the ark, and within the ark are the Ten Commandments. The transfer from one apartment to the other was therefore both a change of ministration and a revelation of the law enthroned at the center of God's government.
Since that opening, light from the commandments has shone out upon God's people with new clearness and force. That light centers the present test upon the Sabbath, by which loyalty to the whole law is proved.