4th Antiphon O Clavis David 20 December
O Key of David and Sceptre of the house of Israel,
you open and none can shut,
you shut and none can open:
Come and bring the captives out of the prison house:
those who sit in darkness and the shadow of death.
The reference is to Isaiah 22:22 and Revelation 3:7. Though the earthly fortunes of the dynasty of David and of the Jewish people may rise or fall, God is the Lord of history, and nothing can prevent the fulfilment of his purposes.