The law appoints men who are weak to be high priests. But after the law had been given, God swore an oath and appointed his Son, who has been made perfect forever.
That’s why the promise comes by faith, so that it can be based on God’s grace and be guaranteed to all of Abraham’s children. That means not only those who are his children under the law, but also those who are Abraham’s children because have the same faith that he did. He is the father of us all.
Some of you are trying to be made right with God by obeying the law. As a result, you’ve been separated from Christ and you’ve fallen away from God’s grace.