O Clavis David

O Key of David and scepter of the House of Israel! who opens and no man shuts, who shuts and no man opens; come, lead the captive from prison, sitting in darkness and the shadow of death.

Here is some commentary from Fr. Mark:

 The antiphon draws its invocation from the twenty-second chapter of Isaiah. The Lord says to Shebna, the master of the household of King Hezekiah, “And it shall come to pass in that day, that I will call my servant Eliakim the son of Helkias, and I will clothe him with thy robe, and will strengthen him with thy girdle, and will give thy power into his hand: and he shall be as a father to the inhabitants of Jerusalem, and to the house of Juda. And I will lay the key of the house of David upon his shoulder: and he shall open, and none shall shut: and he shall shut and none shall open. And I will fasten him as a peg in a sure place, and he shall be for a throne of glory to the house of his father” (Is 22:20-23).