The Epitome of the Divine Institutes

If therefore the Jews have been rejected by God, as the faith due to the sacred writings shows, and the Gentiles, as we see, brought in, and freed from the darkness of this present life and from the chains of demons, it follows that no other hope is proposed to man, unless he shall follow true religion and true wisdom, which is in Christ, and he who is ignorant of Him is always estranged from the truth and from God. Nor let the Jews, or philosophers, flatter themselves respecting the Supreme God. He who has not acknowledged the Son has been unable to acknowledge the Father. This is wisdom, and this is the mystery of the Supreme God. God willed that He should be acknowledged and worshipped through Him. On this account He sent the prophets beforehand to announce His coming, that when the things which had been foretold were fulfilled in Him, then He might be believed by men to be both the Son of God and God.

Nor, however, must the opinion be entertained that there are two Gods, for the Father and the Son are one. For since the Father loves the Son, and gives all things to Him, and the Son faithfully obeys the Father, and wills nothing except that which the Father does, it is plain that so close a relationship cannot be separated, so that they should be said to be two in whom there is but one substance, and will, and faith. Therefore the Son is through the Father, and the Father through the Son. One honour is to be given to both, as to one God, and is to be so divided through the worship of the two, that the division itself may be bound by an inseparable bond of union. He will leave nothing to himself, who separates either the Father from the Son, or the Son from the Father.