Benedict of Nursia, The Rule of St. Benedict (early 6th century)—This set of guidelines for monastic living, written by the abbot of Monte Casino for his own monastery and possibly some neighboring houses, focuses on humility and obedience. Promoting stability and stressing the need to give up all personal property, it offers practical and moderate advice for a community of monks designed to function almost as a family under a fatherly abbot. This rule was the most widely adopted by monasteries throughout medieval Europe from the ninth century onward.

St. Bernard of Clairvaux, Sermons on the Song of Songs (c. 1153)—This unfinished work by the first leader of the Cistercian Order follows the medieval exegetical scheme of fourfold meaning of Scripture: literal, allegorical, moral, and mystical. Themes range from behavior of monks to the mystical union between the Bridegroom (Christ) and...