Catechism of the Catholic Church §1589 — excerpt
Before the grandeur of the priestly grace and office, the holy doctors felt an urgent call to conversion in order to conform their whole lives to him whose sacrament had made them ministers.
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: St. Gregory of Nazianzus, Oratio 2, 71, 74, 73: PG 35, 480-481 · St. John Vianney, quoted in B. Nodet, Jean-Marie Vianney, Cure' d' Ars, 100