Roman Catechism 4.18

Chapter 4 — Part I: The Creed — Article II: And in Jesus Christ, His Only Son, Our Lord

Section 18. "His Only Son" — In these words, mysteries more exalted with regard to Jesus are proposed to the faithful as objects of their belief and contemplation; namely, that He is the Son of God, and true God, like the Father who begot Him from eternity. We also confess that He is the Second Person of the Blessed Trinity, equal in all things to the Father and the Holy Ghost; for in the Divine Persons nothing unequal or unlike should exist, or even be imagined to exist, since we acknowledge the essence, will and power of all to be one. This truth is both clearly revealed in many passages of Holy Scripture and sublimely announced in the testimony of St. John: In the beginning was the Word, and the Word was with God, and the Word was God.