Gregory the Dialogist

But He is Himself alone, and no man can turn away His thought. And what His soul desireth, even that He doeth. Are there not angels and men, the heavens and the earth, the air and the waters of the ocean, all the winged creatures, quadrupeds, and creeping things? And surely it is written, Which God created that they should be. Whereas then there is such a multitude of things in the circle of nature, wherefore is it now said by the voice of the blessed man, He is Himself alone? …

Morals on the Book of Job, Book XVI ↗

Thomas Aquinas

To the objection that this proof which he introduced on the basis of the righteousness of his life is not fitting, he shows as a consequence that the most certain and demonstrative proof cannot be introduced about divine judgments because of the incomprehensibility of the divine will. So he then says, "Truly he is alone," as if to say: There is no other creature like or equal to him who can comprehend him, and consequently his will. …

Commentary on Job ↗

Bonaventure

The fear of the Lord arises in us from the consideration of the perspicacity of divine wisdom. Whence Job: "For he alone is, and no one can turn away his thoughts. And therefore I am troubled at his presence, and when I consider him, I am made fearful with dread." He alone is, that is, from himself alone he has being, and all other things are from him. And just as all things flow from the first being, so God is the cause of all things. …

Collationes de Septem Donis, Collation 2 ↗