He lieth under the shady trees - Referring to his usually inactive and lazy life. He is disposed to lie down in the shade, and especially in the vegetable growth in marshy places on the banks of lakes and rivers, rather than to dwell in the open field or in the upland forest. This account agrees well with the habits of the hippopotamus. The word here and in Job 40:22 rendered “shady trees” (צאלים tse'eliym), is by Gesenius, Noyes, Prof. Lee, and Schultens, translated “lotus,” and “wild lotus.” The Vulgate, Syriac, Rosenmuller, Aben-Ezra, and others, render it “shady trees.” It occurs nowhere else in the Scriptures, and it is difficult, therefore, to determine its meaning. According to Schultens and Gesenius, it is derived from the obsolete word צאל tsā'al, “to be thin, slender;” and hence, in Arabic it is applied to the “wild lotus” - a plant that grows abundantly on the banks of the Nile, and that often serves the wild beasts of the desert for a place of retreat. It is not very important whether it be rendered the “lotus,” or “shades,” though the probable derivation of the word seems to favor the former.
In the covert of the reed - It is well known that reeds abounded on the banks of the Nile. These would furnish a convenient and a natural retreat for the hippopotamus.
And fens - בצה bitstsâh - “marsh, marshy places.” This passage proves that the elephant is not here referred to. He is never found in such places.