The fourth Great Antiphon in the last week of Advent refers to the "Key of David," which is mentioned in another prophecy from the book of Isaiah.
The current translation of the antiphon is below.
O Key of David,
opening the gates of God’s eternal Kingdom:
come and free the prisoners of darkness!
The reference to the "Key of David" is a prophecy from the book of Isaiah.
I will place the key of the House of David on his shoulder;
what he opens, no one will shut,
what he shuts, no one will open.
The original Latin antiphon also talks about the "Scepter" of the House of Israel, which is a reference to the book of Genesis.
The scepter shall never depart from Judah,
or the mace from between his feet,
Until tribute comes to him,
and he receives the people’s obedience.
The Messiah is the one who will open to us the gates of Heaven and free us from our prison of darkness.