What you open, no one can shut

 and what you shut, no one can open.

Day 4 of the O Antiphons:  O Key of David

Artist:  Ansgar Holmburg

Here's a poem by Gerard Manley Hopkins:

Moonless Darkness
Gerard Manley Hopkins.

Moonless darkness stands between.
Past, the Past, no more be seen!
But the Bethlehem-star may lead me
To the sight of Him Who freed me
From the self that I have been.
Make me pure, Lord: Thou art holy;
Make me meek, Lord: Thou wert lowly;
Now beginning, and alway:
Now begin, on Christmas day.