For what the law was powerless to do in that it was weakened by the sinful nature, God did by sending his own Son in the likeness of sinful man to be a sin offering. And so he condemned sin in sinful man, in order that the righteous requirements of the law might be fully met in us, who do not live according to the sinful nature but according to the Spirit. Romans 8:3-4
As good as the law was, it was powerless to conquer sin. This is not because the law was weak; rather it is because of our fallen nature. The New English Bible says that “our lower nature robbed it of all potency.” The law can reveal sin; even stimulate it; but when it comes to overcoming it, our sinful nature undermines its best efforts.
Thanks to God, because what the law could not do, God did by sending his very own Son with a nature that resembled our sinful nature. He came in the “likeness of sinful man.” His mission was to put an end to sin, to condemn its evil power that held the human race captive.
God’s redemptive work in Christ was so that what the law justly demanded of us might be fully satisfied. This righteous requirement is met “in us” not in the sense that we fulfilled its demands but rather that God met it through the sacrificial death of his Son. We no longer must be under the control of a sinful lower nature, but can now are guided and empowered by the Spirit of God.
Now, that is good news!