I think it supports the new testament theme.
Genesis 4:2 tells us that Abel kept flocks as a shepherd and Cain worked the soil, growing produce like fruit. When we think about Adam and Eve, they sinned with the fruit of the garden. Cain brought the Lord some fruit as an offering (Genesis 4:3) from his labors.
Humanity sinned by eating the forbidden fruit. Abel brought the Lord his firstborn fat portions from his flock. God looked favorably on Abel’s offering. What we have offered the Lord is our sin; our labor, we have nothing good to give him. We are like Cain. We think our good works should be good enough for God. They aren't. The Law requires a death penalty for sin.
“All of us have become like one who is unclean, and all our righteous acts are like filthy rags; we all shrivel up like a leaf, and like the wind our sins sweep us away” (Isaiah 64:6).
God says that not only are our sins filthy, but our deeds we estimate to be righteous are considered filthy rags as well.
That is a huge problem.