Gregory the Dialogist

The depths also of the floods He hath searched, and the hidden things He hath brought to light. And because the teachers of the New Testament are brought to this, that even the hidden darkness of allegories in the Old Testament they search out, it is rightly added; The depths also of the floods He hath searched, and the hidden things He hath brought to light. For what else are here called 'floods' but the sayings of the ancient Fathers. …

Morals on the Book of Job, Book XVIII ↗

Thomas Aquinas

For if he can lay the mountains low, if he can cut through rocks and exercise the same power over all the earth, he consequently can see the precious things which are hidden there although the eye of man cannot see them. His eye not only sees those things which lie hidden in the earth, but "he also searches fully the depths of rivers," i.e., he knows what lies hidden in the depths of rivers so perfectly he seems to carefully inspect them, and the sign of this is that, "he has brought hidden things to light," to reveal them to men.

Commentary on Job ↗