At long last God has begun the task of reconciling the whole rebellious world to himself, and the invasion of Paul's life is but one beach-head in the invasion of all enemy territory.
But the most astounding thing was not the fact that the kingdom had now drawn near. The most astounding thing was the nature of the events through which the approach of the kingdom became manifest. For, in Jesus, the Messiah had been disclosed not as a transcendent divine being, immune to sin and death, but as an all-to-human, all-to-sinful, all-to-impotent Galilean, a scandal which reached its acme in the death on the cross. This was the incredible offence which as a Pharisee Paul had righteously resisted; it was the incredible gospel which as an apostle he was impelled to accept and preach! The most horrible event had become through God's own choice the hinge between the ages, the difference between night and day. In the cross of the Messiah, history comes to an end. This does not mean that the kingdom had been fully established but that in the sufferings of the Messiah the powers of the end-time had begun to work. Confronted by this stupendous revelation, Paul was changed from a Pharisee missionary to an apostle of Christ. His dynamic stemmed from this 'unheard-of' event, in which he was called to participate.
from page 93, The Obedience of Faith