Hi ShellBell,
We all agree that Christ's sacrifice cleansed us of past sin.
Rom 3:25
Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God
It was only past sin that was remitted at the cross. Once we receive Christ there is no more sin that can be charged against us (as 1John 3:7-10 says).
Rom 8:33
Who shall lay any thing (this includes sin) to the charge of God's elect? It is God that justifieth
Jesus truly set us free from sin.
John 8:34-36
Jesus answered them, Verily, verily, I say unto you, Whosoever committeth sin is the servant of sin.
And the servant abideth not in the house for ever: but the Son abideth ever.
If the Son therefore shall make you free, ye shall be free indeed.
Other scriptures that confirm 1John 3:7-10 include the following.
1Pet 4:1
Forasmuch then as Christ hath suffered for us in the flesh (crucified), arm yourselves likewise with the same mind (our old man crucified with him, Rom 6:6): for he that hath suffered in the flesh (Rom 6:6) hath ceased from sin;
1Pet 4:18
if the righteous scarcely be saved, where shall the ungodly and the sinner appear?
Here we see 2 different groups described.
Group 1: Righteous and saved
Group 2: Ungodly, sinner, unsaved.
Note there is no 3rd group described as saved sinner.
Gal 2:15
We who are (spiritual) Jews by nature (with circumcision of the heart, Rom 2:28), and not sinners of the Gentiles, (Gentile being unbelievers)
Firstly we should define sin, and this will help to understand why God says Christians cannot be charged with sin.
Sin is:
1: Unbelief in Jesus, John 16:9. This is the sin the world is convicted of. Christians do not commit this sin.
2: Unrighteousness, 1John 5:17. Christians cannot be charged with this sin as our faith is counted for righteousness, Rom 4:5.
3:Transgression of the law, 1John 3:4. Christians cannot be charged with this sin because we are not under the law.
Whatever the law says it says to those under it, Rom 3:19
Scripture tells us many times that we're not under the law.
Rom 8:2
For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
Rom 10:4
For Christ is the end of the law for righteousness to every one that believeth.
Gal 3:24-25
Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.But after that faith is come, we are no longer under a schoolmaster.
Gal 5:18
But if ye be led of the Spirit, ye are not under the law.
Rom 4:15
for where there is no law there is no transgression/Sin
Our faith is counted for righteousness, Rom 4:5. For Christians righteousness is not by works of the law as we're not under the law. Hence Satan the accuser cannot charge us with "sin" (transgression of the law, 1John 3:4).
Rev 12:9-11
So the great dragon was cast out, that serpent of old, called the Devil and Satan, who deceives the whole world; he was cast to the earth, and his angels were cast out with him.
Then I heard a loud voice saying in heaven, “Now salvation, and strength, and the kingdom of our God, and the power of His Christ have come, for the accuser of our brethren, who accused them before our God day and night, has been cast down. And they overcame him by the blood of the Lamb and by the word of their testimony, and they did not love their lives to the death.
Rom 8:33
Who shall lay any thing (this includes sin) to the charge of God's elect? It is God that justifieth
And as for our obvious physical failings that still occur at times, this is not sin that can be charged against us. Also we will not profit by doing wrong either. God disciplines us (consider King David with his adultery/murder).
But we see that our flawed physical body is already "dead (by faith, crucified with Christ, Rom 6:6) because of sin", Rom 8:10. Hence we cannot be charged with sin.
We're a new creation in Christ, 2Cor 5:17
Our life is hid with Christ in God, Col 3:3
Christians abide in Christ and in him there is no sin, 1John 3:5.
To say a Christian "sins" is to say that there is sin in Christ.
I hope this helps.