5 We confess one God, alone unmade, alone eternal, alone unoriginate, alone possessing immortality, alone good, alone mighty, Creator, Ordainer and Disposer of all things, unchangeable and unalterable, righteous and good, of the Law and the Prophets and the New Testament. We believe that this God gave birth to the Only-begotten Son before all worlds, through Whom He made the world and all things, that He gave birth to Him not in semblance, but in truth, following His own will, so that He is unchangeable and unalterable, God's perfect Creature, but not as one of His other creatures, His Handiwork, but not as His other works; not, as Valentinus maintained, that the Son is a development of the Father, nor, as Manichæus has declared of the Son, a consubstantial part of the Father, nor, as Sabellius, who makes two out of One, Son and Father at once, nor, as Hieracas, a light from a light, or a lamp with two flames, nor, as if He was previously in being and afterwards born, or created afresh, to be a Son, a notion often condemned by yourself, blessed Pope, publicly in the Church, and in the assembly of the brethren. But, as we have affirmed, we believe that He was created by the will of God before times and worlds, and has His life and existence from the Father, Who gave Him to share His own glorious perfections. For, when the Father gave to Him the inheritance of all things, He did not thereby deprive Himself of attributes which are His without origination, He being the source of all things.
6. “So there are three Persons, Father, Son and Holy Ghost. God, for His part, is the Cause of all things, utterly unoriginate and separate from all; while the Son, put forth by the Father outside time, and created and established before the worlds, did not exist before He was born, but, being born outside time before the worlds, came into being as the Only Son of the Only Father. For He is neither eternal, nor co-eternal, nor co-uncreate with the Father, nor has He an existence collateral with the Father, as some say who postulate two unborn principles. But God is before all things, as being indivisible and the beginning of all. Wherefore He is before the Son also, as indeed we have learned from you in your public preaching. Inasmuch then as He has His being from God, and His glorious perfections, and His life, and is entrusted with all things, for this reason God is His Source. For He rules over Him, as being His God, since He is before Him. As to such phrases as from Him, and from the womb, and I went out from the Father and have come, if they be understood to denote that the Father extends a part and, as it were, a development of that one Substance, then the Father will be of a compound nature and divisible and changeable and corporeal, according to them; and thus, as far as their words go, the incorporeal God will be subjected to the properties of matter.”
Source: On the Trinity (New Advent)