O Clavis David (December 19)

O Clavis David ("O Key of David") gets sung tonight as the Antiphon upon Magnificat.

O Key of David, and Scepter of the house of Israel; that openeth and no man shutteth, and shutteth, and no man openeth: come, and bring forth from the prisionhouse the captive, who sitteth in darkness and in the shadow of death.

Below is a Latin version of the Magnificat itself.

The text for this antiphon is found in two places in the Scriptures: Isaiah 22 and Revelation 3:

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.

Revelation 3:7: And to the angel of the church in Philadelphia write; These things saith he that is holy, he that is true, he that hath the key of David, he that openeth, and no man shutteth; and shutteth, and no man openeth....

Clearly, the Revelation passage is a direct quoting of the Isaiah; I am not yet certain of the significance of the phrase in either case, however.