In your breviary:
O Key of David O royal power of Israel controlling at your will the gate of heaven: come, break down the prison walls of death for those who dwell in darkness and the shadow of death, and lead your captive people into freedom.
The older, more literal translation:
O Key of David and Scepter of the house of Israel,you open and no man can close, you close and no man can open; Come rescue the prisoners who dwell in darkness and the shadow of death.
The older version calls to mind Matthew 18:18 where Our Lord give the power of the keys--to bind and to loose--to Peter. So here the antiphon reminds us not only that Jesus rescued us from the prison of sin by his redeeming death, but gives us a hint of continuity, as his Church is the vehicle of that saving, liberating grace.
Closing prayer -today's new missal collect.
O God, eternal majesty,whose ineffable Word the immaculate Virgin received through the message of an Angel, and so became the dwelling place of divinity, filled with the light of the Holy Spirit, grant, we pray, that by her example we may in humility hold fast to your will. Through Our Lord, etc...