Augustine of Hippo

"For He spoke, and they were made:" for no other one made those things which are to fear; but He spoke, and they were made. "He commanded, and they were created" [Psalm 33:9]: He commanded by His Word, and they were created.

Exposition on Psalm 33 ↗

Thomas Aquinas

Then when he says, "For he spoke," he shows a twofold effect regarding the earth. First, the effect of creation; second, of governance, at "The Lord brings to naught." In creation, two things are to be considered: namely, the formation itself and the creation itself. Both are present here. For first he shows the formation when he says, "He spoke," and so on. Second, the creation itself, when he adds, "He commanded," and so on. …

Exposition on the Psalms of David ↗

Bonaventure

And so it is clear that possible things come forth from the most actual, changing things from the most stable, and the lowest things from the most sublime. And as the sun by shining brings forth a variety and number of colors, so out of this Word there comes forth a variety of things. Hence there is no understanding except through the Word. …

Collations on the Hexaemeron, Collation 3 ↗