13 With these words I invoke mercy: and if it were possible to propitiate His wrath with whole burnt offerings or sacrifices, I would not even have spared these. Do you also yourselves imitate your trembling priest, you, my beloved children, sharers with me alike of the Divine correction and loving-kindness. Possess your souls in tears, and stay His wrath by amending your way of life. Sanctify a fast, call a solemn assembly, as blessed Joel with us charges you: gather the elders, and the babes that suck the breasts, whose tender age wins our pity, and is specially worthy of the loving-kindness of God.
I know also what he enjoins both upon me, the minister of God, and upon you, who have been thought worthy of the same honour, that we should enter His house in sackcloth and lament night and day between the porch and the altar, in piteous array, and with more piteous voices, crying aloud without ceasing on behalf of ourselves and the people, sparing nothing, either toil or word, which may propitiate God: saying “Spare, O Lord, Your people, and give not Your heritage to reproach,” and the rest of the prayer; surpassing the people in our sense of the affliction as much as in our rank, instructing them in our own persons in compunction and correction of wickedness, and in the consequent long-suffering of God, and cessation of the scourge.
Source: Orations (New Advent)