Matthew Poole and continuators on Job 40:22

22. The shady trees cover him with their shadow, the willows of the brook compass him about.

Or, of Nilus, of which this word is oft used in Scripture. And this seems to be the chief argument by which the learned Bochart proves this to be meant of the Hipopotamus, whose constant residence is in or near the River of Nilus, or the Willows that grow by it. But it is well alledged by our learned and judicious Caryl, that this word Naal is never used to express Nilus when it is put by it self, as here it is but onely where the word Egypt is added to it, as it is in all the places which Bochart produceth. And this very phrase, the Willows of the Brook, is used of other Brooks or Rivers besides Nilus, as Levit. 23. 40. Comp. Isa. 15. 7.