In Galatians three and four, Paul highlights the error of trying to earn righteousness through relying on the Law instead of God’s promises. He parallels the unchangeable nature of man-made covenants like a will to the covenant that God made with Abraham. Wills cannot be altered and neither can God’s way of imputing or gifting His righteousness.
Abraham wasn’t righteous because he earned it, instead God “transferred” His righteousness to Abraham was because He believed what God had promised. A gift is only a gift if it isn’t based on performance and the Law merely pointed out our inability to gain righteousness through performance and our need for a Savior.
For us to gain righteousness through the Law we’d have to flawlessly obey it; a feat unattainable by fallen humans. However, because of love, God sent His Son so that we might become His children; thereby enjoying every benefit of sonship and loving relationship. This also fosters unity since we all need a savior, which effectively removes the common barriers of culture, class and gender.
And since Jesus paid the penalty through “owning” our sin, we too now can “own” His righteous through trusting in His final payment for us. He did for us what the Law never could by making a way for us to enjoy
God’s path for our righteousness:
We can’t earn it. We can’t deserve it. We can’t change it. We can’t improve upon it.
But we CAN receive it by believing God’s promise in Christ!