Agnus Dei (liturgy) Agnus Dei (liturgy) In the Mass of the Roman Rite and also in the Eucharist of the Anglican Communion, the Lutheran Church, and the Western Rite of the Orthodox Church the Agnus Dei is the invocation to the Lamb of God sung or recited during the fraction of the Host. The Syrian custom of a chant addressed to the Lamb of God was introduced into the Roman Rite Mass by Pope Sergius I (687–701) in the context of his rejection of the Council of Trullo (692), which was well received in the Byzantine East and called the Quinisext Council, but
Agnus Dei (liturgy) the Roman Missal, § 83, states: "The supplication "Agnus Dei", is, as a rule, sung by the choir or cantor with the congregation responding; or it is, at least, recited aloud. This invocation accompanies the fraction and, for this reason, may be repeated as many times as necessary until the rite has reached its conclusion, the last time ending with the words "dona nobis pacem" ('grant us peace')." In Tridentine Requiem Masses, the first two invocations ended with "dona eis requiem" (give them rest) instead of "miserere nobis", and the last with "dona eis requiem sempiternam" (give them rest eternal).