Caritate Christi Compulsi §27

²⁷ And even for men individually, penance is the foundation and bearer of true peace detaching them from earthly and perishable goods, lifting them up to goods that are eternal, giving them, even in the midst of privations and adversity, a peace that the world with all its wealth and pleasures cannot give. One of the most pleasing and most joyous songs ever heard in this vale tears is without doubt the famous "Canticle of the Sun" of St. Francis. Now the man who composed it, who wrote it and sang it, was one of the greatest penitents, the Poor Man of Assisi, who possessed absolutely nothing on earth, and bore in his emaciated body the painful Stigmata of His Crucified Lord.