Roman Catechism 3.23

Chapter 3 — Part I: The Creed — Article I: I Believe in God, the Father Almighty, Creator of Heaven and Earth

Section 23. The Name Father Also Discloses The Plurality Of Persons In God — But the pastor should teach that on hearing the word Father, besides the ideas already unfolded, the mind should rise to more exalted mysteries. Under the name Father, the divine oracles begin to unveil to us a mysterious truth which is more abstruse and more deeply hidden in that inaccessible light in which God dwells, and which human reason and understanding could not attain to, nor even conjecture to exist.