
Matt 21:44
For as he is the foundation and corner stone to some, and is set for the rising of them, and to whom he is precious; so he is a stone set for the fall of others, and at which they stumble and fall, and fall upon it: and such are they who are offended at Christ’s state of humiliation on earth; at the manner of his birth, the meanness of his parentage, and education; the despicable figure he made in his person, disciples, and audience; and at his sufferings and death: and these “shall be broken”: as a man that stumbles at a stone, and falls upon it, breaks his head or his bones, at least bruises himself, does not hurt the stone, but the stone hurts him; so all such as are offended at Christ, injure their own souls, being filled with prejudices against him, and contempt and disbelief of him, which if grace prevents not will issue in their everlasting destruction: but whilst there is life, the means of grace continue, the kingdom of God is not taken away; there is hope that such may be recovered from their impenitence and unbelief: “but on whomsoever it shall fall, it will grind him to powder”. Just as if a millstone, or any stone of such like weight and bulk, was to fall upon an earthen vessel; or, as the stone cut out of the mountain without hands, by which the Messiah and his kingdom, are designed, brake in pieces the image in Nebuchadnezzar’s dream, so that it became like the chaff of the summer threshing floor. As the former part of this verse expresses the sin of unbelievers, and the danger they are exposed unto by it, this sets forth their punishment; and has respect both to the vengeance of Christ, on the Jewish nation, at their destruction, which would fall heavy from him in his state of exaltation, for their evil treatment of him in his state of humiliation; and to his severe wrath, which will be executed at the day of judgment on all unbelievers, impenitent Christless sinners, who have both offended him, and been offended at him; when their destruction will be inevitable, their salvation irretrievable, and their souls irrecoverably lost, and ruined.
John Gill
Those persons are said to fall upon Christ, who rush forward to destroy him; not that they occupy a more elevated position than he does, but because their madness carries them so far, that they endeavor to attack Christ as if he were below them. But Christ tells them that all that they will gain by it is, that by the very conflict they will be broken. But when they have thus proudly exalted themselves, he tells them that another thing will happen, which is, that they will be bruised under the stone, against which they so insolently dashed themselves.
John Calvin