5:17 Now Christ makes clear that he is not contradicting the law, but neither is he preserving it unchanged. He comes “to fulfill” it, i.e., he will bring the law to its intended goal. This is what the Pharisees and scribes have missed, who therefore need a greater conformity to God’s standards (v. 20). Both the Law and the Prophets together (v. 17) and the Law by itself (v. 18) were standard Jewish ways of referring to the entire Hebrew Scriptures (our Old Testament).
Fulfillment of Scripture, as throughout chaps. 1–4, refers to the bringing to fruition of its complete meaning. Here Jesus views his role as that of fulfilling all of the Old Testament. This claim has massive hermeneutical implications and challenges both classic Reformed and Dispensationalist perspectives. It is inadequate to say either that none of the Old Testament applies unless it is explicitly reaffirmed in the New or that all of the Old Testament applies unless it is explicitly revoked in the New. Rather, all of the Old Testament remains normative and relevant for Jesus’ followers (2 Tim 3:16), but none of it can rightly be interpreted until one understands how it has been fulfilled in Christ. Every Old Testament text must be viewed in light of Jesus’ person and ministry and the changes introduced by the new covenant he inaugurated. Nor is there any evidence here for the common Christian division of the law into moral, civil, and ceremonial categories or for elevating the Ten Commandments above others. This is not to say that the law cannot or should not be subdivided, but valid divisions will probably require greater thematic nuance and sophistication.
Blomberg, C. (1992). Matthew (Vol. 22, pp. 103–105). Nashville: Broadman & Holman Publishers.