44 Hear how the necessity for the reply arose:— And for this cause did the Jews persecute Jesus, and sought to kill Him, because He did these things on the Sabbath. Their anger was so kindled against Him, that they desired to kill Him, because He did His works on the Sabbath. But let us see also what the Lord answered, My Father works even until now, and I work. Tell us, heretic, what is that work of the Father; since through the Son, and in the Son, are all things, visible and invisible?
You, who are wise beyond the Gospels, have doubtless obtained from some other secret source of learning the knowledge of the Father's work, to reveal Him to us. But the Father works in the Son, as the Son Himself says, The words that I say unto you, I speak not from Myself, but the Father who abides in Me, He does His works. Do you grasp the meaning of the words, My Father works even until now? He speaks that we may recognise in Him the power of the Father's nature employing the nature, which has that power, to work on the Sabbath.
The Father works in Him while He works; without doubt, then, He works along with the working of the Father, and therefore He says, My Father works even until now, that this present work of His words and actions may be regarded as the working of the Father's nature in Himself. This works even until now identifies the time with the moment of speaking, and therefore we must regard Him as referring to that very work of the Father's which He was then doing, for it implies the working of the Father at the very time of His words.
And lest the Faith, being restricted to a knowledge of the Father only, should fail of the hope of eternal life, He adds at once, And I work; that is, what the Father works even until now, the Son also works. Thus He expounds the whole of the faith; for the work which is now, belongs to the present time; and if the Father works, and the Son works, no union exists between them, which merges them into a single Person. But the wrath of the bystanders is now redoubled. Hear what follows, For this cause, therefore, the Jews sought the more to kill Him, because He not only broke the Sabbath, but because He called God His own Father, making Himself equal with God. Allow me here to repeat that, by the judgment of the Evangelist and by common consent of mankind, the Son is in equality with the Father's nature; and that equality cannot exist except by identity of nature.
The begotten cannot derive what it is save from its source and the thing generated cannot be foreign to that which generates it, since from that alone has it come to be what it is. Let us see, then, what the Lord replied to this double outburst of wrath, Verily, verily, I say unto you, the Son can do nothing of Himself, but what He has seen the Father doing: for what things soever He does, these the Son also does in like manner.
Source: On the Trinity (New Advent)