Romans 4:3

What does Scripture say? “Abraham believed God, and it was credited to him as righteousness.”

(v3, NIV)

Here Paul settles the debate. Paul quotes Genesis 15:6 where it talks about Abraham's belief. Righteousness is credited to Abraham from his belief in God. Therefore, nobody can bring the argument that Abraham was justified by works. Thus, they have nothing to say. It is by faith and not by works that one is justified.