Paul begins his letter to the Romans by stating that he is a bondservant of Jesus Christ, called to be an apostle, separated to the gospel of God. He also adds "by the will of God" in most of his other letters to affirm the purpose of his calling to preach the gospel to Jews and Gentiles, something Paul never doubted. So sure was he of his calling and purpose that he gave up his freedom and eventually his life to pursue and fulfill it.