Who hath enjoined him his way? - Who hath prescribed to him what he ought to do? Who is superior to him, and has marked out for him the plan which he ought to pursue? The idea is, that God is supreme and independent; no one has advised him, and no one has a right to counsel him. Perhaps, also, Elihu designs this as a reproof to Job for having complained so much of the government of God, and for being disposed, as he thought, to "prescribe" to God what he should do.
Who can say, Thou hast wrought iniquity? - Thou hast done wrong. The object of Elihu is here to show that no one has a right to say this; no one could, in fact, say it. It was to be regarded as an indisputable point that God is always right, and that however dark his dealings with people may seem, the "reason" why they are mysterious "never is, that God is wrong."

Who hath enjoined him his way - Has God taken instructions from any man how he shall govern the world?
Thou hast wrought iniquity? - Who can prove, in the whole compass of the creation, that there is one thing imperfect, superabundant, or out of its place? Who can show that there is, in the course of the Divine providence, one unrighteous, cruel, or unwise act? All the cunning and wickedness of man have never been able to find out the smallest flaw in the work of God.

Who hath enjoined him his way?.... He teaches men his own ways, the methods of his grace and mercy towards them; and he prescribes to them the ways in which they should walk; but none can lead or prescribe to him; as the way of governing the world, in what manner he should act in it; who has "taught him in the path of judgment?" or "showed to him the way of understanding?" Isaiah 40:14; and particularly whom he should afflict, in what manner he should do it, when and how long he should continue it; all which he does according to his sovereign will, and is not to be controlled: and, in a spiritual sense, no man can or ought to enjoin and prescribe to him whom he should save, and in what way; he saves whom he pleases, and in his own way, even by his Son Jesus Christ, and no other; or "who hath visited", or "should visit on him", or "with him his way" (e)? who can take upon him to examine into his ways, and scrutinize them, and call him to an account for what he does? no man can overlook his ways and works, or censure him for any of his actions:
or, who can say, thou hast wrought iniquity? this may be said of every man, but it cannot be said of God by any without sin; for, as there is no iniquity in his nature, there can be none in his works; not any in his works of providence, no, not in the afflictions of his people; just and true are all his ways.
(e) "quis visitavit super illum viam ejus", Montanus, Michaelis; "cum eo", Tigurine version.

Job dared to prescribe to God what He should do (Job 34:10, Job 34:13).