There are basically two options for what to do with an uneasy conscience. Given that the conscience is uneasy because it registers that you’re not living up to the standards God requires (never mind actually contravening them), and that guilt always attends sin, one common strategy is to put more effort into conforming better to the law.
Of course, the law, summarised in the ten commandments, is holy and just and good, and total conformity to it is only our duty. But when the law comes into contact with a sinner, it can only condemn.
Which means that hauling a guilty conscience to the law, or being driven to the law by a guilty conscience, can bring no relief. The most that the law can do for a sinner is inform them of what God is and expects, and force them to recognise how unable they are to keep it, and heighten their awareness of their sinfulness. Thus the first of the ten commandments requires us to worship God “by thinking, meditating, remembering, highly esteeming, honouring, adoring, choosing, loving, desiring, fearing of him; believing him; trusting, hoping, delighting, rejoicing in him…” but when we’re guilty of not esteeming him as highly as he deserves, all that the law can do is remind us of that fact, and show up the exacerbations of our sin. It can give you no power, no impetus, no ability, to give this required obedience. It is a hard taskmaster.
In the context of the divine revelation as a whole though, one further use of the law is to give sinners a clearer sight of the need they have of Christ. Not that the law can show us where to find him or how to approach him. But a sinner whose contact with the law leaves them with even less hope than they had before still has the possibility of hope, from another source.
The gospel does no injury to the law. It’s not that God is merciful and accepts sinners in spite of our sins. Rather God is merciful and accepts sinners because their sins have been dealt with. Every accusation the law makes against us is true, and can’t be ignored. But come now, saith the Lord, and let us reason together: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.
Instead of an endless round of failing to live up to the law and trying harder and failing again, sinners are invited to leave the service of this taskmaster and subscribe themselves to Christ instead, who his own self bore our sins in his own body on the tree. ‘I have blotted out, as a thick cloud, thy transgressions, and as a thick cloud thy sins: return unto me, for I have redeemed thee.’ Sins thoroughly dealt with, blotted out, put away, the law deprived of the ability to condemn. Sinners don’t need to be perpetual slaves to their own sin, thwarted at every attempt to obey by personal corruption and guilty inability: the power of sin can be broken. The law needn’t be a taskmaster with a scourge to drive unwilling souls to painful attempts at obedience; it is possible to know the law as a friend and guide, and obey it in that spirit.
We can’t stand on our own feet in front of the accusing, condemning law. Surely we know by experience, or else it’s very easily put to the test, that we can’t live up to the law, and our endless failures can’t be lightly written off. The question is only whether we can consent to someone else standing in our place to meet its requirements. That’s admittedly humbling for a sinner too, even if in a different way than the humbling that the law inflicts, but in the balance against relief for the conscience and a new friendly relationship with the law in the hand of the Saviour, not to mention eternal security, it’s a small price to pay.
Prickly, uncomfortable, guilty consciences that won’t stoop to accept the pacifying that Christ offers in the gospel can’t expect to be quieted any other way, and especially won’t find satisfaction in scrabbling to curry favour with the law in the hand of Moses.