How did Christ fulfil the Law?

​ Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfil them.

(Matthew 5:17, Sermon on the Mount)

What did Jesus mean here? How did Christ fulfil the Law? What does that mean for the Law itself?

Christ Fulfilled the Law
The Law can mean: a) God’s decrees, b) Scripture, c) a Covenant, d) the Mosaic Covenant (or Covenant with Israel at Sinai), or e) God’s moral law. Given the context in the Sermon on the Mount it is almost certainly “d,” the Mosaic Law; yet with a twist.

To abolish means to unyoke, as in unyoking an animal from a cart. As such it means to break or destroy what was.

To fulfil means is to be full or to meet.

The Jewish leaders of Jesus’ day feared He was a religious revolutionary who would upset their cherished possession, or rather their misinterpretations and additions (Mt 23:4; Mk 7:7), for Jesus, being perfect, never broke God’s Law. He would be much more radical and still more conservative than they thought.

Christ fulfilled the Law by doing what Adam, doing what the descendants of Abraham, and of Israel and the Kings could not do—be that perfect covenant partner. No human can by their works “fulfil the Laws demands” (“Rock of Ages”).

Christ could fulfil the Law, as Matthew is keen to point out, because He was the lawgiver greater than Moses.

The New Covenant
In fulfilling, or meeting, the demands of previous covenants, Jesus inaugurated the promised New Covenant (Jer 31:31; Ezk 36; Heb 8 et al).Jesus’ life and ministry marked a watershed or transition period between the covenants (it was inter-covenantal). When He died the veil was torn. After He ascended the Spirit was given. There is a newness in the New Covenant. New (kainos) means something new in kind, like a new invention; it isn’t new (neos) as in a new type of car but a new form of travel like a teleporter.  (The NC doesn’t abolish, replace or succeed the Old, it fulfils the promises of the Law and Prophets. It is the direct continuation of God’s plans).

According to Gal 3:15–29 the Law of Moses was temporary and served the purpose of exposing our sin and making the promise to Abraham essential. It also has a guiding quality.

As such certain aspects of the Law of Moses were no longer necessary. Since Christ was the sacrifice for sin and the Holy Spirit now made believers the living temple of His presence the Temple was obsolete and hence the ceremonial system. The dietary laws (an external sign of holiness) were no longer necessary for Christ taught that holiness flowed from Christ’s imputation and through a new heart cleansed from within by the Spirit. (Scripture emphatically declares this in Mk 7:19b, “Thus He declared all foods clean,” c.f. Acts 10). Circumcision as the covenant sign gave way to baptism, the Passover to the Lord’s Supper (Lk 22:20), and so the list could go on.

A Law Remains (The Law of Christ or Moral Law)
How then could Jesus say in Mt 5:18, “For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished.” Likewise, how could he commend the “scribes and Pharisees” pursuit of righteousness, or holiness, (v. 19), and state this legal righteousness was needed to enter the Kingdom? (Truly, Christ is our righteousness and the Spirit enables us to live righteously, thus guaranteeing our place in the Kingdom, both present and eternal).
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In saying that He would fulfil the Law of Moses and yet the law would never pass away Jesus is commending to us the Law of Christ, or the Moral Law (Gal 5:14, 6:2). While the Law of Moses as a whole has been fulfilled in Christ, a law remains which is the moral law found within it (see 2nd London Baptist Confession, ch. 19, for the classic Christian understanding of the threefold division of the Law). This is binding upon all believers to follow as our guide to holiness by the Spirit.