Of the Feast at Which It Was Objected at Once that Christ Ate with Sinners, and that His Disciples Did Not Fast; Of the Circumstance that the Evangelists Seem to Give Different Accounts of the Parties by Whom These Objections Were Alleged; And of the Question Whether Matthew and Mark and Luke are Also in Harmony with Each Other in the Reports Given of the Words of These Persons, and of the Replies Returned by the Lord
63 Once more, we find that Matthew and Mark have given similar accounts of what was said about the children of the bridegroom not fasting as long as the bridegroom is with them, with this exception, that Mark has named them the children of the bridals, while Matthew has designated them the children of the bridegroom. That, however, is a matter of no moment. For by the children of the bridals we understand at once those connected with the bridegroom, and those connected with the bride.
The sense, therefore, is obvious and identical, and neither different nor contradictory. Luke, again, does not say, “Can the children of the bridegroom fast?” but, “Can ye make the children of the bridegroom fast, while the bridegroom is with them?” By expressing it in this method, the evangelist has elegantly opened up the self-same sense in a way calculated to suggest something else. For thus the idea is conveyed, that those very persons who were speaking would try to make the children of the bridegroom mourn and fast, inasmuch as they would [seek to] put the bridegroom to death.
Moreover, Matthew's phrase, “mourn,” is of the same import as that used by Mark and Luke, namely, “fast.” For Matthew also says further on, “Then shall they fast,” and not, “Then shall they mourn.” But by the use of this phrase, he has indicated that the Lord spoke of that kind of fasting which pertains to the lowliness of tribulation. In the same way, too, the Lord may be understood to have pictured out a different kind of fasting, which stands related to the rapture of a mind dwelling in the heights of things spiritual, and for that reason estranged in a certain measure from the meats that are for the body, when He made use of those subsequent similitudes touching the new cloth and the new wine, by which He showed that this kind of fasting is an incongruity for sensual and carnal people, who are taken up with the cares of the body, and who consequently still remain in the old mind.
These similitudes are also embodied in similar terms by the other two evangelists. And it should be sufficiently evident that there need be no real discrepancy, although one may introduce something, whether belonging to the subject-matter itself, or merely to the terms in which that subject is expressed, which another leaves out; provided only that there be neither any departure from a genuine identity in sense, nor any contradiction created between the different forms which may be adopted for expressing the same thing.
Source: The Harmony of the Gospels (New Advent)