What is the latin prayer just as Communion starts?

Wasn’t raised citing it so I never learned it.

Sounds like (forgive me):

Ah you staying…Christe…

Not Lamb of God I don’t think.

I can’t even begin to spell it since I’ve never seen it in print before.

I am flummoxed and ashamed as a 55 yo every Sunday Catholic.

I think you are referring to the Lamb of God in Latin:

Agnus Dei,
quitollis peccata mundi: miserere nobis.
Agnus Dei,
quitollis peccata mundi: miserere nobis.
Agnus Dei,
quitollis peccata mundi: dona nobis pacem

You can hear it sung here

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