In a similar manner, John said: A woman clothed with the sun and with the moon under her feet (Rv 12.1). For by the "sun" is understood the illumination of truth, whereas by the "moon," which wanes when the month is completed, the changeableness of temporal existence. But because the holy Church is protected by the splendor of light from above, she is, as it were, clothed with the sun. But because she despises all temporal things, she tramples the moon under her feet.
Gregory the Great, From Moralia 34.14 [25], 1-15. CCSL 143B: 1750. in Fathers of the Church, Vol. 144, Cassiodorus, St. Gregory the Great, and Anonymous Greek Scholia, Writings on the Apocalypse, Section 24, p. 65 Mark DelCogliano, Trans.