Why did Paul receive a new body of truth from the ascended Lord?
He was delegated to receive that new body of truth because he was given authority as apostle of the Gentiles and responsibility to carry it to the whole Gentile world. His ministry was distinct from the apostles of Israel, and they were not to usurp his authority.
Les explains that Paul was delegated to receive a whole new body of truth from the Ascended Lord and was given the responsibility to take it out to the whole Gentile world. In the passage, Paul says he did not go up to Jerusalem to those who were apostles before him, but went into Arabia and then returned to Damascus. Les points out that the word Arabia in verse 17 connects to chapter 4, verse 25, where Hagar is Mount Sinai in Arabia. Paul never denigrates the authority of the apostles of Israel, but he will not let them usurp his authority as apostle of the Gentiles. This distinction is what to watch for.
Neither went I up to Jerusalem to them which were apostles before me; but I went into Arabia, and returned again unto Damascus.
More Questions
How did Paul receive the doctrine that appears in his letters?
Everything Paul wrote in his letters came by revelation from God, not from attending a seminary in Jerusalem taught by Peter, James and John, and not from picking up their notes or doing research.