134 Now no question implying any contradiction between these accounts rises here, unless it be raised by the circumstance that Matthew, after telling us how the Lord addressed to the Jews this interrogation, “When the lord, therefore, of the vineyard comes, what will he do unto those husbandmen?” adds, that they answered and said, “He will miserably destroy those wicked men, and will let out his vineyard unto other husbandmen, which shall render him the fruits in their seasons.”
For Mark does not record these last words as if they constituted the reply returned by the men; but he introduces them as if they were really spoken by the Lord immediately after the question which was put by Him, so that in a certain way He answered Himself. For [in this Gospel] He speaks thus: “What shall therefore the lord of the vineyard do? He will come and destroy the husbandmen, and will give the vineyard unto others.” But it is quite easy for us to suppose, either that the men's words are subjoined herewithout the insertion of the explanatory clause “they said,” or “they replied,” that being left to be understood; or else that the said response is ascribed to the Lord Himself rather than to these men, because when they answered with such truth, He also, who is Himself the Truth, really gave the same reply in reference to the persons in question.
Source: The Harmony of the Gospels (New Advent)