Is God’s Grace something entirely new and introduced to us in the New Testament in relation to what Jesus did for us on the cross?
Nope.
The first formal mention of God’s Grace was actually in Genesis 6:8 where it’s written “But Noah found grace in the eyes of the LORD.“
But, really, God’s Grace began in the Garden of Eden after Adam and Eve disobeyed God’s command. Instead of killing them on the spot, God killed sinless animals and covered them and their sins with the bloody skins. God Himself atoned for their sins by sacrificing those animals.
Next, we see Abel sacrificing animals from his flock on an altar for his own sins and those after him that walked in God’s ways continued sacrificing and were obedient to Him.
Now, God’s Grace toward Noah saved him from the condemnation that the rest of mankind was to suffer due to their evil inclinations and disobedience. That condemnation was death and separation from God.
Then, we find God’s Grace formalized toward Israel when He had them build a tabernacle and instituted animal sacrifices to atone for the people’s sins. A sinless animal without blemish was killed and its blood shed and sacrificed upon an altar as payment for the sin of the person who brought the sacrifice.
All of this was only temporary as each day, month and year, Israel had to perform these sacrifices to atone for their sins.
When Jesus Christ finally came, He was called “The Lamb of God” by John the Baptist. And indeed, God sent His sinless Son to be a sacrifice for us to atone for our sins and it was a permanent one that didn’t need repeating.
By sacrificing His own Son and calling upon everyone to trust in the faith of His Son, by God’s Grace we are no longer under the condemnation (death and eternal separation) our sins deserve because Jesus atoned for them and all future sins we might commit.
Jesus was resurrected with a glorified spiritual body and we will eventually be given one too. Even though we are saved, no longer condemned for what we deserved by sinning, we live in these fleshly bodies and with our evil inclinations. We still sin but are not condemned by it as long as we continue to trust in the faith of Jesus.
Seeing that this is so, how should we live our lives?
We have been buried with Christ in the likeness of his death and burial and born again alive in the spirit, shall we not put to death the deeds of the flesh along with controlling our evil inclinations and live our lives in obedience to God and a spiritual connection with Him?