A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
eze 31:1THE OVERTHROW OF EGYPT ILLUSTRATED BY THAT OF ASSYRIA. (Eze. 31:1-18)
third month--two months later than the prophecy delivered in Eze 30:20.
eze 31:2Whom art thou like--The answer is, Thou art like the haughty king of Assyria; as he was overthrown by the Chaldeans, so shalt thou be by the same.
eze 31:3He illustrates the pride and the consequent overthrow of the Assyrian, that Egypt may the better know what she must expect.
cedar in Lebanon--often eighty feet high, and the diameter of the space covered by its boughs still greater: the symmetry perfect. Compare the similar image (Eze 17:3; Dan 4:20-22).
with a shadowing shroud--with an overshadowing thicket.
top . . . among . . . thick boughs--rather [HENGSTENBERG], "among the clouds." But English Version agrees better with the Hebrew. The top, or topmost shoot, represents the king; the thick boughs, the large resources of the empire.
eze 31:4waters . . . little rivers--the Tigris with its branches and "rivulets," or "conduits" for irrigation, the source of Assyria's fertility. "The deep" is the ever flowing water, never dry. Metaphorically, for Assyria's resources, as the "conduits" are her colonies.
eze 31:5when he shot forth--because of the abundant moisture which nourished him in shooting forth. But see Margin.
eze 31:6fowls . . . made . . . nests in . . . boughs--so Eze 17:23; Dan 4:12. The gospel kingdom shall gather all under its covert, for their good and for the glory of God, which the world kingdoms did for evil and for self-aggrandizement (Mat 13:32).
eze 31:8cedars . . . could not hide him--could not outtop him. No other king eclipsed him.
were not like--were not comparable to.
garden of God--As in the case of Tyre (Eze 28:13), the imagery, that is applied to the Assyrian king, is taken from Eden; peculiarly appropriate, as Eden was watered by rivers that afterwards watered Assyria (Gen 2:10-14). This cedar seemed to revive in itself all the glories of paradise, so that no tree there outtopped it.
eze 31:9I . . . made him--It was all due to My free grace.
eze 31:10thou . . . he--The change of persons is because the language refers partly to the cedar, partly to the person signified by the cedar.
eze 31:11Here the literal supersedes the figurative.
shall surely deal with him--according to his own pleasure, and according to the Assyrian's (Sardanapalus) desert. Nebuchadnezzar is called "the mighty one" (El, a name of God), because he was God's representative and instrument of judgment (Dan 2:37-38).
eze 31:12from his shadow--under which they had formerly dwelt as their covert (Eze 31:6).
eze 31:13Birds and beasts shall insult over his fallen trunk.
eze 31:14trees by the waters--that is, that are plentifully supplied by the waters: nations abounding in resources.
stand up in their height--that is, trust in their height: stand upon it as their ground of confidence. FAIRBAIRN points the Hebrew differently, so as for "their trees," to translate, "(And that none that drink water may stand) on themselves, (because of their greatness)." But the usual reading is better, as Assyria and the confederate states throughout are compared to strong trees. The clause, "All that drink water," marks the ground of the trees' confidence "in their height," namely, that they have ample sources of supply. MAURER, retaining the same Hebrew, translates, "that neither their terebinth trees may stand up in their height, nor all (the other trees) that drink water."
to . . . nether . . . earth . . . pit-- (Eze 32:18; Psa 82:7).
eze 31:15covered the deep--as mourners cover their heads in token of mourning, "I made the deep that watered the cedar" to wrap itself in mourning for him. The waters of the deep are the tributary peoples of Assyria (Rev 17:15).
fainted--literally, were "faintness" (itself); more forcible than the verb.
eze 31:16hell--Sheol or Hades, the unseen world: equivalent to, "I cast him into oblivion" (compare Isa 14:9-11).
shall be comforted--because so great a king as the Assyrian is brought down to a level with them. It is a kind of consolation to the wretched to have companions in misery.
eze 31:17his arm, that dwelt under his shadow--those who were the helpers or tool of his tyranny, and therefore enjoyed his protection (for example, Syria and her neighbors). These were sure to share her fate. Compare the same phrase as to the Jews living under the protection of their king (Lam 4:20); both alike "making flesh their arm, and in heart departing from the Lord" (Jer 17:5).
eze 31:18Application of the parabolic description of Assyria to the parallel case of Egypt. "All that has been said of the Assyrian consider as said to thyself. To whom art thou so like, as thou art to the Assyrian? To none." The lesson on a gigantic scale of Eden-like privileges abused to pride and sin by the Assyrian, as in the case of the first man in Eden, ending in ruin, was to be repeated in Egypt's case. For the unchangeable God governs the world on the same unchangeable principles.
thou shall lie in . . . uncircumcised--As circumcision was an object of mocking to thee, thou shall lie in the midst of the uncircumcised, slain by their sword [GROTIUS]. Retribution in kind (Eze 28:10).
This is Pharaoh--Pharaoh's end shall be the same humiliating one as I have depicted the Assyrian's to have been. "This" is demonstrative, as if he were pointing with the finger to Pharaoh lying prostrate, a spectacle to all, as on the shore of the Red Sea (Exo 14:30-31).