参考 Gill (esword上的一个commentary）的解释：
在不恰当或不合适的时候，希伯来人有时会用“不能”来表达。

Mar 6:5 - And he could there do no mighty work,.... Or miracle; not that Christ had no power in himself to work miracles, though their unbelief and contempt of him were very great; but it was *not fit and proper* that he should do any there, since such were their prejudices against him: it is an usual way of speaking with the Hebrews, when either it is not "fit" and proper that a thing should be done, or they "will" not do it, to say it cannot be done; see Gen_19:22;
Gen 19:22 你要速速的逃到那城；因为你还没有到那里，我不能做什麽。」因此那城名叫琐珥（就是小的意思）。

and even it is said of God himself, "So that the Lord could no longer bear, because of your evil doings", Jer_44:22.
Jer 44:22 耶和华因你们所作的恶、所行可憎的事，不能再容忍，所以你们的地荒凉，令人惊骇咒诅，无人居住，正如今日一样。

Not but that he could if he would, but he would not; nor was it fit and proper that he should; the same is the sense here: besides, in Mat_13:58 it is said, "he did not many mighty works there"; and so *the Arabic version* here, "and he did not many mighty works there"; he did not think it proper to do any of any great consequence, nor did he.

Wherefore the Jew (u) has no reason to object this to the divinity of Christ, as if there was a want of power in him. Christ is omnipotent, and he has given proof of his almighty power, by the miracles which he has wrought; and though he wrought no mighty work "there", yet he wrought many elsewhere, which sufficiently attest the truth of his proper deity: the emphasis lies upon the word there; though he did not work any considerable miracle in that place, he did in others; which shows, that it was not a defect of power in him, that was the reason of it, but something else; and Matthew gives the reason of it, and says, it was "because of their unbelief": not that their unbelief was an over match for his power; he could have removed that, if he had thought fit, but he did not do it; he, who is the author and finisher of faith, could have took away their unbelief, as the man that brought his dumb child to Christ, concluded he could; and therefore said to him, "Lord, help my unbelief", Mar_9:24.

Christ sometimes required of the persons he was about to heal, faith in him, that he could heal them; and so did his apostles, Mat_9:28.

Not that faith contributed any thing to the cure, but it was the way and means in which Christ was pleased to communicate his healing virtue;

besides, when persons applied to him for healing, and expressed their faith in him, it gave him an opportunity of working a miracle for that purpose; but now these people did not so much as ask such a favour of him, and so gave him no occasion of doing any mighty work; for which reason it may be said, he could not, no opportunity offering;

and moreover, seeing they disbelieved him, and rejected him as the Messiah, they were unworthy of having any wrought among them; and it was but just and right, to do none; nay, it was rather an instance of kindness not to do any among them; since had he, and they had remained impenitent and unbelieving, as he knew they would, these would have been aggravations of their condemnation.