He controls and contains all things; and it is written: ‘In him all things consist, whether seen or unseen, and he is before all things’ (Col. 1:16-17).
But the creatures are in the places which have been assigned to them: sun, moon, and the other lights in the firmament, angels in heaven and men upon the earth.
[…] The Son is not a creature, because he is not in places assigned to him, but is in the Father, and because he is everywhere even while he is outside all things.
It follows that the Spirit cannot be a creature, for he is not in places assigned to him, but fills all things and yet is outside all things.
Thus it is written: ‘The Spirit of the Lord hath filled the world’ (Wis. 1:7).
And David sings, ‘Whither shall I go from thy Spirit?’ (Psalm 137:7), inasmuch as he is not in any place, but outside all things and in the Son, as the Son is in the Father.
[…] The Son, like the Father, is creator; for he says: ‘What things I see the Father doing, these things I also do’ (John 5:19). ‘All things’, indeed, ‘were made through him, and without him was not anything made’ (John 1:3).
But if the Son, being, like the Father, creator, is not a creature; and if, because all things were created through him, he does not belong to things created; then, clearly, neither is the Spirit a creature.
For it is written concerning him in the one hundred and third Psalm: ‘Thou shalt take away their spirit, and they shall die and return to their dust. Thou shalt put forth thy Spirit, and they shall be created, and thou shalt renew the face of the earth’ (Psalm 103:29-30).
As it is thus written, it is clear that the Spirit is not a creature, but takes part in the act of creation.
The Father creates all things through the Word in the Spirit; for where the Word is, there is the Spirit also, and the things which are created through the Word have their vital strength out of the Spirit from the Word.
Thus it is written in the thirty-second Psalm: ‘By the Word of the Lord the heavens were established, and by the Spirit of his mouth is all their power’ (Psalm 32:6).
Athanasius of Alexandria (c.293-373): Letters to Serapion 3, 4-5, pp.173-174.