This is a c14 text attributed to Pope Innocent VI, here translated by Harry Hagan and set by Mozart. (You may feel a looming problem approaching.)
The Latin text is:
Ave, verum corpus
natum de Maria Virgine,
Vere passum immolatum
in Cruce pro homine,
Cujus latus perforatum
unda* fluxit (et)* sanguine,
Esto nobis praegustatum
in mortis examine.
You can find an English translation for sense here. The OCP version can be purchased here and Hagan’s translation is in their preview. You can access a free version of the sheet music here.
So BIAB takes on Mozart. Not the best idea I’ve ever had – too fast, too shrill.
Better to listen to these.