If this is so, then what is it that shows sin today? How do we know what sin is as the bible tells us it is breaking the law. If the law has no place in the new covenant then why does God write it in our hearts as it is written:
Jer 31:33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
Paul explains this in his letter to the Corinthians:
2Co 3:3 Forasmuch as ye are manifestly declared to be the epistle of Christ ministered by us, written not with ink, but with the Spirit of the living God; not in tables of stone, but in fleshy tables of the heart.
While the law was on stone it only condemned us as we all have broken it which is sin still to this day it is sin to break it. But when God puts the law on our hearts we obey as it is written:
Rom 2:11 For there is no respect of persons with God.
Rom 2:12 For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law;
Rom 2:13 (For not the hearers of the law are just before God, but the doers of the law shall be justified.
Rom 2:14 For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves:
Rom 2:15 Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another
So clearly having the law on the heart is seen by the fruit of obeying that law actually doing it by nature. why? Because we become partakers of the Divine nature as Peter said:
2Pe 1:3 According as his divine power hath given unto us all things that pertain unto life and godliness, through the knowledge of him that hath called us to glory and virtue:
2Pe 1:4 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.
Gods Power in Christ Jesus transforms the sinner into a saint, the disobedient into obedient by his grace.
For when we were Carnal the law was a prison house which brought death and no hope. But to those who are filled with the Spirit the law is fulfilled within us as it is written:
2Co 3:6 Who also hath made us able ministers of the new testament; not of the letter, but of the spirit: for the letter killeth, but the spirit giveth life.
2Co 3:7 But if the ministration of death, written and engraven in stones, was glorious, so that the children of Israel could not stedfastly behold the face of Moses for the glory of his countenance; which glory was to be done away:
2Co 3:8 How shall not the ministration of the spirit be rather glorious?
2Co 3:9 For if the ministration of condemnation be glory, much more doth the ministration of righteousness exceed in glory.
2Co 3:10 For even that which was made glorious had no glory in this respect, by reason of the glory that excelleth.
and again:
Rom 8:3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
Rom 8:4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
So we see that the ministration of the letter on stone kills as the stone has no power to change the sinner but only condemn. But the Spirit is more glorious as it has power to change the sinner and the law is thus fulfilled in us. We no longer walk in the sins of the flesh but in obedience as it is written:
Rom 6:15 What then? shall we sin, because we are not under the law, but under grace? God forbid.
Rom 6:16 Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness?
Rom 6:17 But God be thanked, that ye were the servants of sin, but ye have obeyed from the heart that form of doctrine which was delivered you.
Rom 6:18 Being then made free from sin, ye became the servants of righteousness.
We have been delivered from sin/law breaking and have become servants of the righteousness of the law by faith as it is written again:
Rom 2:26 Therefore if the uncircumcision keep the righteousness of the law, shall not his uncircumcision be counted for circumcision?
Rom 2:27 And shall not uncircumcision which is by nature, if it fulfil the law, judge thee, who by the letter and circumcision dost transgress the law?
This is the good news. Sin is sin and the law shows what sin is by showing what righteousness is:
Rom 3:20 Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.
Doing away with the law would mean there is no sin and no need of a saviour. Jesus did not come to take away the law/righteousness but rather to take away sin. For where there is no sin/transgression there is no condemnation as it is written:
Rom 5:13 (For until the law sin was in the world: but sin is not imputed when there is no law.
and again:
1Jn 3:7 Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous.
1Jn 3:8 He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.
1Jn 3:9 Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
So it is that the good news is not simply forgiveness but power as it is written:
Rom 1:16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
What does that power do?
Rom 1:4 And declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead:
What does the resurrection power do?
Rom 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
Rom 6:5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
Rom 6:6 Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
Rom 6:7 For he that is dead is freed from sin.
Rom 6:8 Now if we be dead with Christ, we believe that we shall also live with him:
Rom 6:9 Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over him.
Rom 6:10 For in that he died, he died unto sin once: but in that he liveth, he liveth unto God.
Rom 6:11 Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.
Rom 6:12 Let not sin therefore reign in your mortal body, that ye should obey it in the lusts thereof.
Rom 6:13 Neither yield ye your members as instruments of unrighteousness unto sin: but yield yourselves unto God, as those that are alive from the dead, and your members as instruments of righteousness unto God.
Rom 6:14 For sin shall not have dominion over you: for ye are not under the law, but under grace.
So then it is clear that the Gospel is the power of God to transform the sinner/law breaker into a righteous person/law keeper. This is the work of God as the law on stone had no power to transform us but only condemn us. By looking to Jesus we become changed into his image by his power as it is written:
2Co 3:17 Now the Lord is that Spirit: and where the Spirit of the Lord is, there is liberty.
2Co 3:18 But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord.
So then the law does indeed play a part in the new covenant. It is a gift through the Lord Jesus unto salvation from sin. Thus we know that sin shall never rise again. as those who will be in the kingdom know the power of God to deliver from sin. Blessings.