Catechism of the Catholic Church §1216 — excerpt
"This bath is called enlightenment, because those who receive this [catechetical] instruction are enlightened in their understanding . . " Having received in Baptism the Word, "the true light that enlightens every man," the person baptized has been "enlightened," he becomes a "son of light," indeed, he becomes "light" himself:
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. Justin, Apol. 1, 61, 12: PG 6, 421 · St. Gregory of Nazianzus, Oratio 40, 3-4: PG 36, 361C