Based upon John the Baptist's reference in John 1:29 to Jesus ("Behold the Lamb of God that taketh away the sin of the world"), the text in Latin is:
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, you who take away the sins of the world, have mercy upon us. Lamb of God, you who take away the sins of the world, have mercy upon us. Lamb of God, you who take away the sins of the world, grant us peace.
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, you who take away the sins of the world, have mercy upon us. Lamb of God, you who take away the sins of the world, have mercy upon us. Lamb of God, you who take away the sins of the world, grant us peace.