His lasting spiritual influence lies in the influence he had on monastic life throughout Europe. Many who heard his eloquent preaching were drawn to the Cistercian order. He personally helped found over sixty abbeys, including Rievaux (N. Yorks) in 1132, Whitland (Dyfed) in 1140, Mellifont (Co. Louth) in 1142 and Boxley (Kent) in 1146.
He was stylish and clear writer: over 300 letters, sermons and treatises survive, for example: "On the Love of God", "The Song of Songs", "On Consideration" (on papal duties), "In praise of the Virgin Mary", and "The life of St. Malachy of Armagh".
He taught simplicity: "God alone", reflected in the strong unadorned architecture of Cistercian abbeys (no gargoyles!). Through faith and prayer he sought to combine the spiritual life with the practical life.