Why did Paul set aside his background in Judaism and legalism?
Paul set aside his background in Judaism and legalism so that he could be totally the preacher of God's grace. Grace is unmerited favor, so reliance on legalistic credentials had to be relinquished for him to proclaim God's unmerited favor alone.
Les teaches that Paul had to put all that background in Judaism and legalism aside so that he could be totally the preacher of God's grace. The reason was not to add grace to legalism, but to be wholly given to grace. Les reminds us that grace is unmerited favor, meaning Paul's former religious background and legal standing could not be the basis of his message. He had to set it all aside so that his ministry would be centered entirely on God's grace.