What is the meaning of Matthew 5:17-18?

17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil. 18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled. (Matthew 5:17-18 KJV)

Thomas Scott’s Commentary

Verses 17-18: Various opinions seem to have prevailed about the changes which would take place under the Messiah; and many who supposed Jesus to be the Messiah, and had heard some parts of his doctrine, were ready to conclude that he meant wholly to set aside the ancient religion, and to establish an entirely new one in its place; which tended to mislead some and prejudice others.

But he assured them that he did not “come to destroy the law or the prophets;” or to teach any thing inconsistent with the true meaning of their sacred writings, which would still continue in force as a part of divine revelation. His design was not to “destroy,” but to “fulfill.” It was evident from Moses and the prophets themselves, that the ritual law was “a shadow of good things to come;” and Christ was come to fulfill the intent of it, and to hold forth the truths and blessings typified by it in a plainer manner.

The moral law he came to fulfill, by perfectly obeying it as the Surety of his people, by his life, suffering, death, and doctrine; to establish it in its fullest honor and authority, and to make the most effectual provision for men’s loving and obeying it. So that, as long as the word endured, not the least word, or letter, or point, or comma, so to speak, of the whole law, should by any means lose its authority, or fail of answering the end for which it was given; and the moral law would, to the end of time, continue the standard of sin and holiness to all men, and the believer’s rule of duty; for Jesus came to accomplish the design of the introductory dispensation, and not to counteract or subvert it.—‘Christ came not to bring a new way of righteousness and salvation into the world, but to fulfill that indeed which was shadowed by the figures of the law, by delivering men through grace from the curse of the law; and moreover to teach the true use of obedience which the law appointed, and to grave in our hearts the force of obedience.’—Beza.

The phrase (“till all be fulfilled”) occurs, importing the performance of what was typified by the law, and foretold by the prophets. Mt 24:34; Mr 13:30; Lu 21:32 —Whitby. The fulfillment therefore of legal types, and the prophecies of the Old Testament concerning the Messiah and his kingdom, must be intended, as well as the establishment of the moral law in full honor and authority. In another passage Lu 22:16 a still more emphatical word is employed in a similar connection, which fully confirms the above interpretation.