A portion of a letter written by Augustine of Hippo (354-430) to Faltonia Proba, a widow of the wealthiest man in the Roman Empire. She had asked him about prayer. He wrote a letter to her which has become a classic on prayer.
I haven’t forgotten your request, and what I promised you, to write you about praying to God… I can’t tell you what great joy your request gives me, for I see what real concern you have about prayer. Can you not realize that there can be no worthier occupation as a widow than prayer? As the Apostle admonishes: “a woman who is a true widow in her desolation, wholly trust in the Lord, giving all her days and nights to prayer.” It might seem strange to have prayer as your first priority, when you are noble and rich from a worldly perspective, and indeed the mother of so many children. But you are spiritually wise enough to recognize living in this world, with this kind of life, no heart can be free from anxiety.
Letters of Faith Through the Seasons, James M. Houston, Honor Books, 2006, vol. 1, p. 272. The letter of Augustine on prayer in this volume is “a paraphrased series of selections from his long response” on prayer.