Why was Paul's sufficiency not because of his background?
Paul’s sufficiency came from God, not from himself. Although he was highly educated, sat under the greatest rabbi, and was a Pharisee of the Pharisees, he refused to rely on those credentials. He counted them worthless, even dung, so he could become Christ’s workmanship and a humble servant of the Creator God.
Les explains that Ephesians 4 declares we are not sufficient of ourselves to think anything as of ourselves, but our sufficiency is of God. He reminds listeners that Saul of Tarsus was highly educated, the most educated Jew of his day, having sat at the feet of the greatest rabbi, and a Pharisee of the Pharisees. Though he could have claimed qualification by training, he never did. In Philippians he called all that dung and cast it aside as worthless, so he might become the very workmanship of Christ Himself. His sufficiency was therefore not because he was a Hebrew of the Hebrews or a Pharisee of the Pharisees, but because he was a humble servant of the Creator God. Les also notes these verses illustrate the difference between law and grace.