William Burkitt on Mark 12:9

These words of our Saviour are taken out of the 118th Psalm, which the Jews understood to be a prophecy of the Messiah, and accordingly Christ applies them to himself: the church is the building intended, Christ himself the stone rejected.

The rejecters, or the builders rejecting, are the heads of the Jewish church; that is the chief priest and pharisees. God, the great master-builder of his church, takes this precious foundation-stone out of the rubbish, and sets it in the head of the corner. Nevertheless, there are many that stumble at this stone; some through ignorance, others through fear and malice: some are offended at his person, others at his doctrine.

These shall be broken in pieces; but on whomsoever this stone shall fall, it will grind them to powder; that is, Christ himself will fall as a burdensome stone upon all them that knowingly and malicoiusly oppose him; and particularly upon the Jews; who not only rejected, but persecuted and destroyed him.

Thus Christ tells the Chief Priests and Pharisees their particular doom, and also declares what will be the fatal issue of all that opposition which is made against himself and his church; it will terminate in the inevitable destruction of all its opposers; Whosoever shall fall on this stone shall be broken; and on whomsoever it shall fall, it will grind them to powder.