What were the purposes of the Mosaic law?

Question 10019.

The Mosaic law occupies six hundred and thirteen commandments, three biblical books, and a fair amount of Christian confusion, and the confusion usually begins with a wrong assumption: that the law was given as a ladder to heaven. It was not. Paul asks our exact question, “Why then the law?” (Galatians 3:19), and Scripture’s answers are rich, specific, and liberating. Understanding the purposes of the Mosaic law will save you from legalism on one side, lawlessness on the other, and a muddled Bible in between.

What the Law Was Never For

Clear the ground first: the Mosaic law was never a means of justification. “By works of the law no human being will be justified in his sight, since through the law comes knowledge of sin” (Romans 3:20). Israel at Sinai was already a redeemed people; the Ten Commandments open not with a demand but a memorial: “I am the LORD your God, who brought you out of the land of Egypt” (Exodus 20:2). Redemption preceded requirement; grace preceded law even at Sinai. Abraham had been counted righteous by faith four hundred and thirty years earlier, and Paul’s whole argument in Galatians 3 is that the later covenant could not annul the earlier promise (Galatians 3:17-18). Anyone teaching that Old Testament saints were saved by law-keeping and New Testament saints by faith has misread both Testaments; salvation has always been by grace through faith, a point I established in What is dispensationalism?.

So the law is not a ladder. What, then, is it? Scripture assigns it at least five deliberate functions.

A Constitution, a Mirror, and a Fence

First, the Mosaic law was Israel’s national constitution: the covenant charter organising a redeemed people into “a kingdom of priests and a holy nation” (Exodus 19:5-6), governing worship, courts, calendar, diet, land, and family for one nation in one land under one King. Its statutes displayed God’s wisdom before the watching world: “what great nation is there, that has such righteous statutes?” (Deuteronomy 4:8). Second, it was a mirror: “through the law comes knowledge of sin” (Romans 3:20); “if it had not been for the law, I would not have known sin” (Romans 7:7). A mirror shows the dirt; it cannot wash a single spot, and it was never meant to. Third, it was a fence: by marking Israel off from the nations in food, dress, and calendar, the law preserved the messianic line and the revelatory deposit from pagan absorption, “the dividing wall of hostility” that stood until Messiah came (Ephesians 2:14). Distinctiveness was not snobbery; it was quarantine for the sake of the world’s coming Blessing.

Each function was glorious; none was permanent in administration. Constitutions govern nations, mirrors serve mornings, fences guard growing seasons.

A Guardian Pointing to Christ

The fourth purpose crowns the others: “the law was our guardian until Christ came, in order that we might be justified by faith” (Galatians 3:24). The word paidagogos describes the household slave who supervised a child until maturity: strict, temporary, and aimed at handover. The law tutored Israel, and through Israel humanity, in lessons no lecture could teach: the holiness of God, taught in graded degrees of access, courts, veils, and a Most Holy Place entered once a year; the deadliness of sin, taught in the daily bleeding of substitutes at the altar; and the shape of the coming redemption, taught in type after type, the Passover lamb, the scapegoat, the mercy seat, the high priest. Every sacrifice preached the same sermon: sin means death, a substitute may die in your place, and “it is impossible for the blood of bulls and goats to take away sins” (Hebrews 10:4), so look beyond the shadow to the substance. The law, rightly read, was Israel’s daily gospel rehearsal, and its fifth purpose follows: to shut every mouth, “that every mouth may be stopped… For by works of the law no human being will be justified” (Romans 3:19-20), driving the convicted straight to mercy.

This is why the Lord Jesus could say the Scriptures “bear witness about me” (John 5:39) and why Philip could preach Christ from Moses. The guardian’s whole curriculum was a portrait of the Son.

The Law and the Christian Now

What, then, is the believer’s relationship to the Mosaic law today? Paul’s answer is administrative, and it is definite: “you are not under law but under grace” (Romans 6:14); Christ is “the end of the law for righteousness to everyone who believes” (Romans 10:4); the guardian’s term expired when the Heir came of age (Galatians 3:25). The Mosaic covenant was a package, and it is not dismembered into keepable thirds; the believer is not under its ceremonies, its civil code, or Sinai’s administration of its moral commands. Does that abolish morality? The opposite: the moral character of God expressed at Sinai is re-expressed in “the law of Christ” (Galatians 6:2), taught by the apostles, written on the heart under the New Covenant I described in my New Covenant article, and empowered by the indwelling Spirit, “in order that the righteous requirement of the law might be fulfilled in us, who walk not according to the flesh but according to the Spirit” (Romans 8:4). Nine of the ten commandments reappear in the epistles as Christian instruction; the sabbath alone does not, transposed instead into the rest we have in Christ (Colossians 2:16-17; Hebrews 4).

So the Christian reads the law as fulfilled Scripture, not binding administration: profitable, all of it, “for teaching, for reproof, for correction” (2 Timothy 3:16), revealing God’s character and Christ’s glory on every page, while our marching orders come from the risen Lord through His apostles. Under grace does not mean under nothing; it means under a better covenant, a better Mediator, and a better power.

The Law in Israel’s Future

One dispensational footnote about the Mosaic law completes the picture. The prophets describe Millennial worship with temple, sacrifice, and feast, Ezekiel 40-48 in detail, and readers ask how sacrifices can return if Calvary is final. The answer lies in what sacrifices always were: effectual signs, not effectual payments. As the Lord’s Supper looks back to the cross without repeating it, Israel’s Millennial offerings will memorialise the once-for-all sacrifice at the centre of her national worship, “a statute forever” finding its ceremonial setting under the New Covenant’s administration. The law’s ceremonial vocabulary, in other words, has a commemorative future, purged of shadow-status, in the kingdom where the Lamb Himself is present. Nothing in that arrangement competes with Hebrews; memorials never compete with the events they honour.

Meanwhile the law’s deepest ambition, God’s standards written not on tablets but on hearts, is being realised in every believer the Spirit indwells (Jeremiah 31:33; 2 Corinthians 3:3). Sinai’s stone always pointed to this flesh-and-blood edition.

Reading the Mosaic Law as a Christian

Let me give you a working method for the next time your reading plan lands you in Exodus 21 or Leviticus 13, because under grace does not mean skipping. Ask three questions of any statute. What does this reveal about God? Every command is a window: the gleaning laws reveal His heart for the poor, the parapet law His concern for ordinary safety, the sacrificial detail His holiness and the costliness of approach. What does this anticipate of Christ? The Mosaic law is the richest picture gallery in Scripture: trace the high priest’s garments, the two birds of the leper’s cleansing, the red heifer, and you are tracing profiles of the Saviour, “the law has but a shadow of the good things to come” (Hebrews 10:1). And what abiding principle of righteousness does this express? The command not to muzzle the threshing ox becomes, in Paul’s hands, the principle that workers deserve wages (1 Corinthians 9:9-10); the case laws are worked examples of love for God and neighbour, on which the whole law hangs (Matthew 22:37-40).

Read this way, the Mosaic law becomes what Psalm 119 found it: sweeter than honey, a lamp and a light, without ever becoming again the covenant administration you live under. The psalmist’s delight and Paul’s “not under law” are not in tension; the one describes the word’s character, the other your covenant position. I find believers who master this distinction gain the whole Old Testament back: no longer a legal minefield to tiptoe past, but six hundred and thirteen windows into the character of the God who has now written His law on their hearts. That, after all, was the destination all along: not law abolished, and not law re-imposed, but law internalised by the Spirit of the Son. Moses himself would call that the better country he saw from Nebo.

So, now what?

Read the Mosaic law this month the way its Author intended: as mirror, hold your conscience to it and let it drive you to Christ, never to self-salvage; as portrait gallery, hunt the pictures of Jesus in Passover, priesthood, and mercy seat; and as covenant history, honouring the guardian without re-enrolling under it. Refuse both classroom errors: the legalist repeating a course Christ has completed for you, and the antinomian burning the textbooks of holiness. You are under grace, indwelt by the Spirit, apprenticed to the law of Christ. Is the righteous requirement of the law being fulfilled in your walk, not by your straining, but by His Spirit?

“So then, the law was our guardian until Christ came, in order that we might be justified by faith. But now that faith has come, we are no longer under a guardian.” (Galatians 3:24-25, ESV)