What does Galatians 3:7 mean?

This teaches us about the cornerstone in Christian theology that gives emphasis on the importance of faith in establishing spiritual lineage and identity. It implies that faith in Christ is what truly makes someone a child of Abraham, symbolically speaking. Abraham himself was chosen not because of his works or his ethnic background, but because of his faith in God. This sets a precedent that it is not our actions or our heritage that justify us before God but our faith.