Romans 4 “13 It was not through the law that Abraham and his offspring received the promise that he would be heir of the world, but through the righteousness that comes by faith. 14 For if those who depend on the law are heirs, faith means nothing and the promise is worthless, 15 because the law brings wrath. And where there is no law there is no transgression.
16 Therefore, the promise comes by faith, so that it may be by grace and may be guaranteed to all Abraham’s offspring—not only to those who are of the law but also to those who have the faith of Abraham. He is the father of us all.
22 This is why “it was credited to him as righteousness.” 23 The words “it was credited to him” were written not for him alone, 24 but also for us, to whom God will credit righteousness—for us who believe in him who raised Jesus our Lord from the dead. 25 He was delivered over to death for our sins and was raised to life for our justification.”

Abraham was righteous not by the law but by grace through faith.

Righteousness is by faith in Jesus because He died for our sins and was raised to make us righteous by GRACE.

The old covenant (law) was a temporary covenant for Israel from 1500BC to AD30 when it was abolished on the cross.

Ephesians 2:14-16 “For he himself is our PEACE, who has made the two groups one and has destroyed the barrier, the dividing wall of hostility, by SETTING ASIDE in HIS FLESH the LAW with its COMMANDS and regulations. His purpose was to create in himself one new humanity out of the two, thus making peace, and in one body to reconcile both of them to God through the CROSS,”
The entire law (10 commandments + 603 laws) were abolished on the cross.

So now believers are Righteous by Faith in Jesus and not works of the law.

Romans 10:4 “CHRIST is the END of the LAW so that there may be RIGHTEOUSNESS for everyone who BELIEVES.”