O Key of David and sceptre of Israel, what you open no one else can close again; what you close no one can open. 

O come to lead the captive from prison; free those who sit in darkness and in the shadow of death.       

The key was a symbol of authority (as we see, for example, in Matthew 16, 19 – “[Jesus said to Peter, “I will give you the keys of the kingdom of heaven, and whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.”) The key was worn over the shoulder. 

The holder of the key in the palace has the authority to grant or to deny access to the royal presence. Referring immediately to Eliakim, son of Hilkiah, God says: “I will place on his shoulder the key of the house of David: he shall open, and no one shall shut; he shall shut and no one shall open” (Is. 22,22). 

Our antiphon is, clearly, an almost exact quotation of this verse. Isaiah also writes: “..a child has been born for us, a son given to us; authority rests upon his shoulders…” (9.6). Christian tradition has always seen this prophecy as fulfilled in Christ. When, in the Apostles’ Creed, we say “he descended into hell”, and when Christian authors talk about the “harrowing of hell”, they are referring to the role of God’s Son, who unlocks for us the gate of heaven.