Catechism of the Catholic Church §1974 — excerpt
The evangelical counsels manifest the living fullness of charity, which is never satisfied with not giving more. They attest its vitality and call forth our spiritual readiness.
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. Francis de Sales, Love of God 8, 6