The poem is from Their Music is Mary:Selected Poems from Queen of All Hearts Magazine by the Montfort Fathers (Montfort Publications).
At Mass With the Blessed Virgin Mary
A cloud of witnesses assembles near
The altar, yet not seeking Aaron's rod
In blossom; theirs to behold in mystic rite
The immolation of the Lamb of God.
Around the Virgin Mother of the Lamb
(The snow recedes before her purity)
They gather unafraid, her motherhood
Their welling peace, their sweet security.
No sound is heard, but soon anointed hands
Will hold the Anointed One he bids come forth
Into this world, as once at Bethlehem
When countless angels hailed the sacred birth.
Now Mary leads the choirs of th' assembled throng,
One hundred thousand thousand voices cry,
"Lord God of hosts, accept our sacrifice;
Send blessings on Thy people, Adonai."
- Louise Manning, r.c.
I selected it as appropriate for this Feast, even though the reference to Bethlehem in stanza three is unexpected and theologically counter-intuitive.