During the coronation mass traditionally held at the Reims Cathedral, the phrase is spoken by the officiating archbishop just before the distribution of Holy Communion. The archbishop elevates the Host and addresses the newly anointed monarch and congregation, saying “Ecce Agnus Dei, ecce qui tollit peccata mundi” (Behold the Lamb of God, behold Him who takes away the sins of the world).

The Agnus Dei is a standard section of the Ordinary of the Catholic Mass, which was set to elaborate polyphonic choral and orchestral music for royal coronations throughout European history.