Hugh Thomas Henry,
Catholic Encyclopedia
(1913)
“ Qui tollis peccata mundi, suscipe deprecationem nostram; Qui sedes ad dexteram Patris, miserere nobis", containing all the words of the original formula of the Agnus Dei, we may find the immediate source of its text. Its remoter source was the declaration of the Baptist: "Ecce Agnus Dei, ecce Qui tollit peccatum mundi" (John, i, 29) , supplemented by the cry of the two blind men (Matt. ix, 27) : "Miserere nostri, fili David." The scriptural origin of the formula is therefore evident at a glance. ”
