The vision Paul had on the road to Damascus was no passing emotion, but a vision that had very clear and emphatic directions for him, and he says, "I was not disobedient to the heavenly vision." Our Lord said, in effect, to Paul – Your whole life is to be overmastered by Me; you are to have no end, no aim, and no purpose but Mine. "I have chosen him."
When we are born again we all have visions, if we are spiritual at all, of what Jesus wants us to be, and the great thing is to learn not to be disobedient to the vision, not to say that it cannot be attained. It is not sufficient to know that God has redeemed the world, and to know that the Holy Spirit can make all that Jesus did effectual in me; I must have the basis of a personal relationship to Him. Paul was not given a message or a doctrine to proclaim, he was brought into a vivid, personal, overmastering relationship to Jesus Christ. Verse 16 is immensely commanding – "to make thee a minister and a witness." There is nothing there apart from the personal relationship. Paul was devoted to a Person not to a cause. He was absolutely Jesus Christ’s, he saw nothing else, he lived for nothing else. "For I determined not to know anything among you, save Jesus Christ, and Him crucified."