135 More serious difficulty, however, may be created by the fact that Luke not only does not speak of them as the parties who made that answer (for he, as well as Mark, attributes these words to the Lord), but even represents them to have given a contrary reply, and to have said, “God forbid.” For his narrative proceeds in these terms: “What therefore shall the lord of the vineyard do unto them? He shall come and destroy these husbandmen, and shall give the vineyard to others.
And when they heard it, they said, God forbid. And He beheld them, and said, What is this then that is written, The stone which the builders rejected, the same has become the head of the corner?” How then is it that, according to Matthew's version, the men to whom He spoke these words said, “He will miserably destroy those wicked men, and will let out this vineyard unto other husbandmen, which shall render him the fruits in their seasons;” whereas, according to Luke, they gave a reply inconsistent with any terms like these, when they said, “God forbid”?
And, in truth, what the Lord proceeds immediately to say regarding the stone which was rejected by the builders, and yet was made the head of the corner, is introduced in a manner implying that by this testimony those were confuted who were gainsaying the real meaning of the parable. For Matthew, no less than Luke, records that passage as if it were intended to meet the gainsayers, when he says, “Did ye never read in the scriptures, The stone which the builders rejected, the same has become the head of the corner?”
For what is implied by this question, “Did ye never read,” but that the answer which they had given was opposed to the real intention [of the parable]? This is also indicated by Mark, who gives these same words in the following manner: “And have ye not read this scripture, The stone which the builders rejected has become the head of the corner?” This sentence, therefore, appears to occupy in Luke, rather than the others, the place which is properly assignable to it as originally uttered.
For it is brought in by him directly after the contradiction expressed by those men when they said, “God forbid.” And the form in which it is cast by him—namely, “What is this then that is written, The stone which the builders rejected, the same has become the head of the corner?”— is equivalent in sense to the other modes of statement. For the real meaning of the sentence is indicated equally well, whichever of the three phrases is used, “Did ye never read?” or, “And have ye not read?” or, “What is this, then, that is written?”
Source: The Harmony of the Gospels (New Advent)