A formula recited thrice by the priest at Mass (excepting on Good Friday and Holy Saturday) and occurring shortly before Communion near the end of the Canon and after the prayer “Haec commixtio,” etc. The priest repeats thrice, “Agnus Dei, qui tollis peccata mundi” (Lamb of God, Who takest away the sins of the world), twice, adding “miserere nobis” (have mercy on us) and the third time, “dona nobis pacem” (grant us peace), and in Requiem Masses or “miserere nobis” substitutes “dona eo [ea, eis] requiem” (grant him [her, them] rest) the third time adding the word “sempiternam” (eternal rest). He strikes his breast at each repetition excepting in a Requiem Mass when he keeps his hands clasped. The formula is based on the words found in John, 1, and its symbolism is traced through more than thirty references in the Apocalypse. It appears to have been introduced into the Mass about the end of the 6th century when it was sung only once by the clergy and people, and later twice. In the 12th century it appears in its present form, although many churches retained the older “have mercy on us” for the third ending, a custom still kept in the Basilica of Saint John Lateran, Rome. The variation in the Requiem Mass is traced back to the 12th century. Before giving Holy Communion during or outside of Mass, the priest elevates a particle of the Host before the faithful, saying “Ecce Agnus Dei, ecce qui tollit peccata mundi; Domine non sum dignus,” etc. At the end of the Litany of the Saints and the Litany of Loretto the formula appears “Agnus Dei, qui tollis peccata mundi, Parce nobis Domine” (Spare us, O Lord), then “Exaudi nos, Domirte” (Graciously hear us, O Lord) and finally “Miserere nobis.” In the Litany of the Holy Name of Jesus the name Jesu is added to the last word, and Jesu is substituted for Domine in the two previous endings.