Under the Law, man was righteous only if he obeyed all the commandments:

• this includes the 613 commandments of Moses AND
• the many impossible demands of Christ in the 3 synoptic Gospels (sell everything, don’t lust, don’t get angry, forgive others, forsake everything, cut off eye/hand that sins, etc…)

The Law cannot save anyone because we have all sinned.

The law can only give righteousness only based on man’s perfect obedience. Nobody could be perfect except Jesus Christ  Himself.

Romans 10 “4 For Christ is the fulfillment of the law for righteousness to everyone who believes. 5 For Moses writes about the righteousness of the law, “The one who does them will live by them.”

“But the righteousness which is of faith says this, …..“The word is near you, in your mouth, and in your heart;” that is, the word of faith which we preach: 9 that if you will confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved. 10 For with the heart, one believes resulting in righteousness; and with the mouth confession is made resulting in salvation. 11 For the Scripture says, “Whoever believes in him will not be disappointed.”

Jesus alone lived the perfect life for our sake and died for our sins to fulfill the law.

Christ alone rose from the dead to save us.

So if we believe in Christ (trust in Him and not our works) then we are made righteous by His obedience.