We are going to begin in Romans 3:1-4. This is a scripture that has been used to imply that, because the Word of God has been given to Israel (including the Jews), they are the ones that we should look to for authority regarding interpretation and practice of the Old Testament scriptures.
Notice especially, right at this point, "for what if some did not believe?" Now who else could He be referring to there, than the Jews? Is it possible that they might have given a wrong example to the world regarding things that are important to the destiny to which we are called? That is, those things that have to do with the commands of God—and obedience to those commands.
Does that make God's Word any less true? Well, of course it does not! As He said, "Will their unbelief make the faithfulness of God without effect? Certainly not! "Indeed, let God be true. . ." We have to look to the Word of God—not men.