Catechism of the Catholic Church §826 — excerpt
Charity is the soul of the holiness to which all are called: it "governs, shapes, and perfects all the means of sanctification."
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: LG 42 · St. Therese of Lisieux, Autobiography of a Saint, tr. Ronald Knox (London: Harvill, 1958) 235