Matthew 21:42

42. Jesus saith unto them Our Lord now proceeds to hint to them that their first question, with which they opened this debate, was, as has just been said, completely answered. Still under a figure that of a stone rejected, he indicates how he, though by them rejected, would ultimately prove to be Lord of all, whose judgment would grind them to powder. The stone which the builders rejected Psalms 118:22. Note the rapid yet harmonious changes of our Lord’s illustration of the stone. The same stone is first a rejected stone; then, second, a head corner-stone; then, third, a stumbling-stone; and lastly, a stone hurled from a balista.

The stone which the builders reject is one which the architect or workman thinks too unshapely to be worked into the structure, and so casts it off; and this pictures Christ rejected by the Jewish rulers. The head stone of the corner is the large stone placed in the corner of a stone edifice, for the purpose of binding the two walls firmly together. And this describes Christ in his exaltation in the kingdom of God. Our Lord here interrupts the transition of the figure to declare, from Psalm cxviii, that this exaltation of himself was from God; and thus their question as to his authority is completely answered.