Shorter Catechism Qs. 40–42

Q. 40. What did God at first reveal to man for the rule of his obedience?

A. The rule which God at first revealed to man for his obedience, was the moral Law.

Q. 41. Wherein is the moral Law summarily comprehended?

A. The moral Law is summarily comprehended in the ten commandments.

Q. 42. What is the sum of the ten commandments?

A. The sum of the ten commandments is, to love the Lord our God with all our heart, with all our soul, with all our strength, and with all our mind; and our neighbor as ourselves.


Exodus 20:1–17; Deuteronomy 5:7–21; Psalm 119:97, 119:9, 11; Matthew 22:37–40; 1 Timothy 1:8


If you haven’t read the lesson on Q. 39, you should read it first.

Many Christians are very ambivalent about God’s Law. We know legalism is bad, even if we can’t quite define it. So we surmise any teaching that advocates God’s Law is bad. The problem, then, is that we cannot make sense of the psalmists extolling God’s Law. Nor can we make sense of Paul who said, “the law is good, if one uses it lawfully.”

The mistake is equating legalism with the Law. The Old Testament and the New Testament have not even a hint of legalism in them. Legalism is something the guilty man brings to the Law. The Law, as given by God and taught in the Scriptures, is neither legalistic nor is its intent to produce legalism in us.

There have been, of course, and in some places continue to be, those who taught that the OT believers were saved by their careful observance of God’s Law (I'm referring to some forms of Dispensationalism here). Their understanding is truly legalistic, for legalism is the sinner’s attempt to secure his standing before God on the basis of his keeping of God’s Law. But the gospel puts an end to all such thinking. Abraham (an OT believer) was justified by his faith (see Romans 4). The New Testament, of course, makes this abundantly clear (e.g. Eph 2:8–9). He is a legalist who believes and lives, whether consciously or unconsciously, in fear that he may not be doing enough to placate God’s wrath. He is always worried about his relationship with God, or he finds enormous boost of confidence if he’s done something “right.” You know the drill. It’s because the legalistic person cannot rest in the finished work of Christ alone, for himself, obviously, but for others as well, that he demands from others more than faith in Christ’s atoning work before he is satisfied with their sincerity or repentance.

And it is not legalism to love the God who speaks through the Law. Believers longing to express their gratitude for God’s grace toward them in Jesus Christ through obedience is not being legalistic (think about “obedience of faith” in Rom 1:5). Obedience that results from faith is rather the mark of our adoption and a grateful act of worship.

The Ten Commandments give us the essence of that grateful obedience in a summary fashion. Remember that the Decalogue (Ten Commandments) was given to Israel after God had delivered them out of bondage. God’s gracious redemption came before Israel’s grateful obedience. And with the Decalogue God gave Israel sacrifices and the Mercy Seat. They were not left to fend for themselves on the basis of their performance. Mercy and grace were literally written into their religion. So no one should think the Decalogue was given for us to earn our salvation through them. It was rather the divine prescription for a grateful life of worship in covenant with their Lord.

In the weeks to come we will be studying the Decalogue in some detail. But for now remember what Jesus said in Matthew 22:37–40. Thankfully, God hasn’t made loving him a vacuous and mystical experience. The Law is nothing other than a way to love God and our neighbors. In that way God’s Law is both the standard of, and the prescription for, loving God and our neighbors. So, how are we doing on that account? That is, how are we doing with the Decalogue? Do you know what the Decalogue is? Do you think about how to live in obedience of what it commands and avoid what it forbids? That is, love has both positive and negative aspects, on the one hand giving to the beloved beautiful and beneficial things, and on the other hand withholding from the beloved dangers and hurtful things. Lord willing, we will do it together, giving thanks to him for Jesus Christ, and trusting the Holy Spirit will give us the strength.