[Olog-hai]

Don’t misinterpret Hebrews 8:13. Sin is defined by the law of God still, according to the New Covenant; the rest of the New Testament makes that plain, and it’s filled with admonitions against falling away from grace.

[Jim W N]

Under the New Covenant "falling away from grace" IS going back to the law for your salvation and righteousness.

Christ is become of no effect unto you, whosoever of you are justified by the law; you are fallen from grace.

Galatians 5:4.

Notice grace is higher than the law. You must fall from grace to go back to the law.

As far as sin goes, under the New Covenant of grace, the Lord has wiped away the sins of the whole world because of the cross (2 John 2:2). Under the New Covenant of grace, because of the perfect work of Christ on the cross, God says, 'their sins and iniquities will I remember no more" (Heb. 8:12, 10:17)/.

God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them

2 Cor 5:19.