The creative power of God is common to the whole Trinity and belongs to the essence of God.
God is the Father of the Son from eternity; while He is the Father of the creature in time.
Reference: Summa Theologica Volume 1: Treatise on the creation: The mode of emanation of things from the first principle: Whether to create is proper to any person?
To the Father is appropriated power which is chiefly shown in creation, and therefore it is attributed to Him to be the Creator. To the Son is appropriated wisdom, through which the intellectual agent acts; and therefore it is said “Through Whom all things were made.” And to the Holy Ghost is appropriated goodness, to which belong both government bringing things to their proper end, and the giving of life – for life consists in a certain interior movement.
“God is the cause of things by His intellect and will, just as the craftsman is cause of the things made by his craft. Now the craftsman works through the word conceived in his mind, and through the love of his will regarding some object. Hence also God the Father made the creature through His Word, which is His Son; and through His Love, which is the Holy Ghost.” [Page 510]
To create belongs to God according to His being, that is His essence and this is common to the three persons. Hence to create is proper to the whole Trinity, and not only to one of the Persons.
Reference: Summa Theologica Volume 1: Treatise on the Most Holy Trinity: Of the person of the Son:
Word implies relation to creatures. For God by knowing Himself, knows every creature.
The knowledge of God is cognitive and operative of creatures “He spake, and they were made.” Because in the Word is implied the operative idea of what God makes.