73 We have established this point to exclude the idea that after silence God spoke to the Son, or after ignorance the Son began to know. To reach our intelligence terms must be used applicable to our own nature: thus we do not understand communication except by word of mouth, or comprehend the opposite of nescience except as knowledge. Thus the Son does not know the day for the reason that He does not reveal it: the Father, He says, alone knows it for the reason that He reveals it to the Son alone.
But, as we have said, Christ is conscious of no such natural impediments as an ignorance which must be removed before He can come to know, or a knowledge which is not His before the Father begins to speak. He declares the unity of His nature, as the only-begotten, with the Father, by the unmistakable words, All things whatsoever the Father has, are Mine. There is no mention here of coming into possession: it is one thing, to be the Possessor of things external to Him; another, to be self-contained and self-existent.
The former is to possess heaven and earth and the universe, the latter to be able to describe Himself by His own properties, which are His, not as something external and subject, but as something of which He Himself subsists. When He says, therefore, that all things which the Father has, are His, He alludes to the divine nature, and not to a joint ownership of gifts bestowed. For referring to His words that the Holy Spirit should take of His, He says, All things whatsoever the Father has are Mine, therefore said I, He shall take of Mine: that is, the Holy Spirit takes of His, but takes also of the Father's: and if He receives of the Father's, He receives also of His.
The Holy Spirit is the Spirit of God, and does not receive of a creature, but teaches us that He receives all these gifts, because they are all God's. All things that belong to the Father are the Spirit's; but we must not think that whatever He received of the Son, He did not receive of the Father also; for all that the Father has belongs equally to the Son.
Source: On the Trinity (New Advent)