John Newton (d. 1807) wrote a helpful letter which is now called “On the Right Use of the Law.” It is basically Newton’s theological commentary on 1 Timothy 1:8. After discussing the law/gospel distinction, natural laws, and moral laws, he gives some ways the law is used lawfully and some ways in which it is used unlawfully. Here they are in abbreviated form:
1) It is not a lawful use of the law to seek justification and acceptance with God by our obedience to it; because it is not appointed for this end, or capable of answering it in our circumstances. The very attempt is a daring impeachment of the wisdom of God – for if righteousness could come by the law, then Christ has died in vain (Gal. 2:21; 3:21). Therefore, such a hope is not only groundless, but sinful; and, when persisted in under the light of the gospel, it is no less than a willful rejection of the grace of God.
2) It is an unlawful use of the law – and abuse both of law and gospel – to pretend that its accomplishment by Christ releases believers from any obligation to it as a rule. Such an assertion is not only wicked, but absurd and impossible in the highest degree: for the law is founded in the relation between the Creator and the creature, and must unavoidably remain in force so long as that relation subsists. No true believer can deliberately admit a thought or a wish of being released from his obligation of obedience to God, in whole or in part; this thought is an abhorrence to him.
3) The law is lawfully used as a means of conviction of sin. For this purpose the law was promulgated at Sinai. The law entered that sin might abound – not to make men more wicked, though occasionally and by abuse it has that effect, but to make them sensible how wicked they are. Having God’s law in our hands, we are no longer to form our judgments by the maxims and customs of the world…but are to try every principle, temper, and practice by this standard.
4) We use the law lawfully when we use it as a mirror to behold the glory of God. We see the perfection of his excellence of the law in his (Jesus’) life. God was glorified by his (Christ’s) obedience as a man. What a perfect character did he exhibit! Yet it is no other than a transcript of the law.
5) Another lawful use of the law is to consult it as a rule and pattern by which to regulate our spirit and manner of life. The grace of God, received by faith, will disposed us to obedience in general. But, through remaining darkness and ignorance, we are much at a loss as to particulars. We are therefore sent to the law, that we may learn how to walk worthy of God.
6) Finally, we use the law lawfully when we improve it as a test whereby to judge of the exercise of grace. Believers differ so much from what they once were, and from what many still are, that, without this right use of the law, comparing themselves with their former selves, or with others, they would be prone to think more highly of their attainments than they ought.
In summary, the law is used wrongly in a legalist or antinomian way; it is used rightly when we see God’s perfection and glory in it, when we use it as a rule of gratitude, when we use it to see if our faith is true, and when we use it to keep us humble. Newton ends the letter like this:
“Clearly to understand the distinction, connection, and harmony between the law and the Gospel, and their mutual subserviency to illustrate and establish each other, is a singular privilege, and a happy means of preserving the soul from being entangled by errors on the right hand or the left.”