The shady trees - Probably the "lote-trees;" see the note at Job 40:21. The same word is used here.
The willow-trees of the brook - Of the "stream," or "rivulet." The Hebrew word (נחל nachal) means rather "a wady;" a gorge or gulley, which is swollen with torrents in the winter, but which is frequently dry in summer; see the notes at Job 6:15. Willows grew commonly on the banks of rivers. They could not be cultivated in the desert; Isaiah 15:7.

The willows of the brook compass him - This would agree well enough with the hippopotamus.

The shady trees cover him with their shadow,.... Under which it lies, as in Job 40:21; which is thought not so well to agree with the elephant, since, according to Aelianus (h) and other writers, it lies not down, at least but rarely, but sleeps standing; it being very troublesome to it to lie down and rise up again; and besides it is represented by some authors (i) as higher than the trees, and therefore this is supposed to agree better with the river horse; especially since it follows,
the willows of the brook compass him about; or the willows of the Nile, as some choose to render it; which would put it out of all doubt that the river horse is intended, if it could be established, it being an inhabitant of that river; and yet the above writer (k) speaks of elephants, when grown old, seeking large thick and shady woods to take up their abode in.
(h) Ibid. (Aelian. de Animal.) c. 31. (i) Ibid. l. 7. c. 6. (k) Ibid. c. 2.

shady trees--Translate: "lotus bushes."

Brook - Or, of the Nile, of which this word is often used in scripture. His constant residence is in or near this river, or the willows that grow by it.