Catechism of the Catholic Church §929 — excerpt
By a "life perfectly and entirely consecrated to [such] sanctification," the members of these institutes share in the Church's task of evangelization, "in the world and from within the world," where their presence acts as "leaven in the world."
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: Pius XII, Provida Mater · PC 11 · CIC, can. 713 # 2