15 Again, any one who is in doubt concerning this matter may gain from the Jews an accurate knowledge of Christ's nature; or rather learn that He was truly born from the Gospel, where it is written, Therefore the Jews sought the more to kill Him because He not only broke the Sabbath, but said also that God was His own Father, making Himself equal with God. This passage is unlike most others in not giving us the words spoken by the Jews, but the Apostle's explanation of their motive in wishing to kill the Lord.
We see that no plea of misapprehension can excuse the wickedness of these blasphemers; for we have the Apostle's evidence that the true nature of Christ was fully revealed to them. They could speak of His birth:— He said that God was His Father, making Himself equal with God. Was not His clearly a birth of nature from nature, when He published the equality of His nature by speaking of God, by name, as His own Father? Now it is manifest that equality consists in the absence of difference between those who are equal.
Is it not also manifest that the result of birth must be a nature in which there is an absence of difference between Son and Father? And this is the only possible origin of true equality; birth can only bring into existence a nature equal to its origin. But again, we can no more hold that there is equality where there is confusion, than we can where there is difference. Thus equality, as of the image, is incompatible with isolation and with diversity; for equality cannot dwell with difference, nor yet in solitude.
Source: On the Trinity (New Advent)