April 19 (Good Friday) - "Agnus Dei"

Agnus Dei, qui tollis peccata mundi, miserere nobis. Agnus Dei, qui tollis peccata mundi, miserere nobis. Agnus Dei, qui tollis peccata mundi, dona nobis pacem.

which means:

Lamb of God, who takes away the sins of the world, have mercy upon us. Lamb of God, who takes away the sins of the world, have mercy upon us. Lamb of God, who takes away the sins of the world, grant us peace.