Catechism of the Catholic Church §1028 — excerpt
Because of his transcendence, God cannot be seen as he is, unless he himself opens up his mystery to man's immediate contemplation and gives him the capacity for it.
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. Cyprian, Ep. 58, 10, 1: CSEL 3/2, 665