“In the same way then, there has also come to be at the present time a remnant according to God’s gracious choice. But if it is by grace, it is no longer on the basis of works, otherwise grace is no longer grace.” Romans 11:5-6
In the context of Romans, the Jews would have themselves be saved on the basis of their flesh/works. Because they are of Abraham, and because they are circumsized and such, they view themselves to be worthy of salvation. But God determined that long ago salvation would not be on the basis of works, but rather on the basis of a gracious gift to those who have faith. Paul often talks about the faith of Abraham to illustrate this. Though God does not save on the basis of fleshly things, we know that God has not outright rejected the Jews because Paul says there is a remnant of Jews who will receive Grace. Who is the remnant or how is one determined to be among this group? They are or will be the ones who believe and put their faith in Jesus. If salvation was granted simply because of a man’s birth and works of the flesh, then salvation would no longer be by grace. And since we are all sinners, including the Jews, we all need the salvation that is a gift on the basis of faith. Therefore, if you would have God’s favor, follow Jesus Christ.