And he dwelleth - Or rather, "therefore he shall dwell." As a consequence of his opposing God, and devoting himself to a life of sensuality and ease, he shall dwell in a desolate place. Instead of living in affluence and in a splendid city, he shall be compelled to take up his abode in places that have been deserted and abandoned. Such places - like Petra or Babylon now - became the temporary lodgings of caravans and travelers, or the abodes of outcasts and robbers. The meaning here is, that the proud and wicked man shall be ejected from his palace, and compelled to seek a refuge far away from the usual haunts of men.
Which are ready to become heaps - Which are just ready to tumble into ruin.

He dwelleth in desolate cities - It is sometimes the fate of a tyrant to be obliged to take up his habitation in some of those cities which have been ruined by his wars, and in a house so ruinous as to be ready to fall into heaps. Ancient and modern history afford abundance of examples to illustrate this.

And he dwelleth (r) in desolate cities, [and] in houses which no man inhabiteth, which are ready to become heaps.
(r) Though he build and repair ruinous places to gain fame, yet God will bring all to nothing, and turn his great prosperity into extreme misery.

And he dwelleth in desolate cities,.... This is either a continuation of the account of the wicked man's prosperity, which makes him haughty; such is his might and power, that he destroys cities and palaces, built and enjoyed by others, and then out of the ruins of them builds greater cities and more noble palaces, to perpetuate his name to posterity; which sense agrees with Job 3:14; and with the Targum,
"and he makes tabernacles in desert cities, that he may dwelt in houses which were not inhabited;''
and so Ben Gersom: and hence because of his success among men, and the grandeur he lives in, his heart is lifted up, and his hand is stretched out against God; or else this may express the sinful course of life such a man lives, who chooses to dwell in desolate places, and deserts, to do harm to others, to seize upon travellers as they pass by, and rob and plunder them of their substance, sitting and waiting for them in such places, as the Arabians in the wilderness, Jeremiah 3:2; which is the sense of some, as Aben Ezra observes; or rather this points at the punishment of the wicked man, who though for the present may be in great prosperity, possessed of large cities and stately palaces, "yet" or "but" (a), for so the particle may be rendered, "he dwelleth in desolate cities"; in such as shall become desolate, being destroyed by a superior enemy, that shall come upon him; or through his subjects forsaking him, not being able to bear his tyranny and cruelty; or he shall be driven from his dominions by them, and be obliged to fly, and dwell in desert places; or he shall choose to dwell there, through the horrors of a guilty conscience; or, best of all, he shall be reduced to such distress and poverty, that he shall not have a house fit to dwell in; but "shall inhabit the parched places in the wilderness, in a salt land, and not inhabited", Jeremiah 17:6; as follows:
and in houses which no man inhabiteth, which are ready to become heaps; such as have been deserted by their former inhabitants, because come to decay, and ready to fall down upon them, and become heaps of stones and rubbish.
(a) So the Annotator of the Assembly of Divines.

The class of wicked here described is that of robbers who plunder "cities," and seize on the houses of the banished citizens (Isaiah 13:20). Eliphaz chooses this class because Job had chosen the same (Job 12:6).
heaps--of ruins.

But - This is fitly opposed to the prosperity last mentioned, and is the beginning of the description of his misery.