Ambrose, bishop of Milan, is one of the most important figures in fourth-century Church history. The spiritual father of Augustine, Ambrose became one of the most beloved bishops in the history of the Church and one of the four doctors of Western Christianity. Throughout his episcopacy Ambrose cared deeply about the poor and challenged Christians to show the same compassion for others that God had shown them in Jesus Christ. In his encyclical On the Duties of the Clergy, Bishop Ambrose exhorts Christian leaders to be imitators of God and examples to their fellow-believers.
38. Mercy is also a good thing because it makes people perfect, in that it imitates the perfect Father. Nothing graces the Christian soul so much as mercy; mercy first of all toward the poor, as sharers with you in the produce of nature, which generates the fruits of the earth for use by all. Thus freely give what you have to the poor, and help your brother and companion. You give a coin; the one you help receives life. You give money; but it is everything to the recipient. For that person, your denarius constitutes all his property.
39. In this regard, the person you help bestows more on you than you on him, since your salvation may depend on him. When you clothe the naked, you clothe yourself with righteousness. When you bring a stranger under your roof, when you support the needy, that person acquires the friendship of the holy ones and eternal dwelling places for you [Luke 19:9]. That is no small favor. You sow material things and reap spiritual things. Do you wonder at the judgment of God in the case of holy Job? Wonder rather at his virtue, in that he could say: “I was an eye to the blind, and a foot to the lame. I was a father to the poor. Their shoulders were made warm with the skins of my lambs. The stranger dwelt not at my gates, but my door was open to every one that came” [Job 29:15-16, 31:20, 32]. You are clearly blessed if no poor person ever goes away from your house with empty hands. And no one is more blessed than the one who understands the needs of the poor and the distress of the weak and indigent.
 Gregory, Jerome, Ambrose, and Augustine. These four were recognized by the Church for their particularly strong contribution to Christian doctrine.
 St. Ambrose, On the Duties of the Clergy, 1.11.38-39, modified from Everett Ferguson, Inheriting Wisdom: Readings for Today from Ancient Christian Writers (Peabody: Hendrickson Publishers, 2004), 71-72 and St. Ambrose: Select Works and Letters, in A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, 2nd series, vol. 10, ed. Philip Schaff (Edinburgh: T&T Clark, 1997), 7.