If you were to choose one phrase to describe yourself, what would it be? One might argue that, for the apostle Paul, it would be this: "a bondservant of Jesus Christ." He uses it repeatedly to describe his privileged status as a disciple of Jesus, bound to exclusive, absolute, willing obedience. But there was a time when he would have been the last person on earth to embrace and employ such a title. What made "a blasphemer, a persecutor, and an insolent man" adopt the posture of Christ's bondservant?

The change occurred just outside Damascus. Paul was travelling to the city intent upon doing violence to the followers of Jesus of Nazareth. Suddenly a light from heaven shone around him and he fell to the ground. Who knows what went through his mind at that moment? What did he expect? No doubt the persecutor believed that he was doing the will of God; perhaps he even anticipated some divine commendation. Instead a voice spoke to the man lying on the earth: "Saul, Saul, why are you persecuting me?" What a shudder must have gone through the heart of that proud man. There is already a new humility in his confused question: "Who are you, Lord?" Then these words of staggering reality give the crushing answer: "I am Jesus." We might wonder how Paul survived the shock: that imposter, the cursed Nazarene, is the Lord of glory. "I am Jesus, whom you are persecuting. It is hard for you to kick against the goads." He had known and perhaps been bested by Stephen, heard his pointed and powerful sermon and seen his face at his death; he had listened to the believing confessions of tortured followers of the Way; he had studied endlessly the testimonies of the Hebrew Scriptures, his treasured scrolls. And now he is confronted and cast down by the very Messiah that he has been anticipating, the very Messiah that he has been persecuting.

No wonder he was "trembling and astonished." Stripped of all self-righteousness, all self-confidence, his entire world up-ended by this striking moment of divine revelation, he bows his head and asks a question: "Lord, what do you want me to do?"

That question gives us an insight into a humbled heart; it shows us a disciple's disposition. Certainly there is still much pondering and praying for Paul over the coming hours, but this phrase opens a door by which we can gaze into a bondservant's soul. Here is the subordination of one's own will to the will of another. Here is a posture of voluntary humility and ready obedience.

Paul's response is personal. He is face to face with Christ, and there is no thought of anyone else. His relationship to this Jesus is all that now matters. He is concerned not about what he himself would like to do, what others would have him do, or what others should themselves do. "What do you, Christ Jesus, want me, Saul of Tarsus, to do?" Every other allegiance, legitimate or otherwise, assumes its relative and proper obscurity next to the claims of Christ.

His response is immediate. This may be the most complete and radical change of plan in the history of the world. What the Christ speaks will be the rule of his life from this moment. No other plans or purposes will come into the equation, and nothing will be put off to a more convenient occasion. The risen Lord has declared himself, and instantly this man asks only what is required of him. All Paul's hopes, schemes and dreams - short, middle and long term - are instantly abandoned, and all he is and has are put at the immediate disposal of the Lord Christ.

His response is unconditional. Paul has no idea what Jesus of Nazareth will ask of him. Who can say what his command will demand? But that is not the issue. The possible answers do not prevent or inhibit the question. The sense of his question implies this: "Anything and everything that you might require I stand ready to give." This is not some strutting boast, but an unavoidable declaration in the light of who it is that stands before Paul.

His response is voluntary. It is a conscious and willing response. This is a deliberate act of consecration, an offering up of himself with a ready heart. There is no coercion, only felt obligation. This is not an accidental attitude, but a purposeful seeking out of the will of Christ in order to do it.

And so his response is fundamentally active. There is an immediate awareness that this Messiah will require and be entitled to a life lived to the praise of his glory, a life in which everything is given not anaemically but vigorously, not dragged out under duress but poured out exultantly. The living follows the birthing, the doing follows the saving.

And what is the source of this outlook? From where does this disciple's disposition arise?

It is a believing response to Jesus of Nazareth, the risen Lord and God's Christ: "I am Jesus." It is the unparalleled and unparellelable glory of his unalloyed divinity and glorious humanity that has captured Paul's heart. It is Jesus as the promised Prophet, Priest and King; the Son of David; the one Mediator between God and man; the Redeemer of God's elect; the Hope of Israel; the Light of nations; the Dayspring from on high; the Lord of lords and King of kings. Paul has opposed him with every fibre of his being, and he has responded with sovereign mercy. When Paul later writes that "he loved me and gave himself for me" he is speaking of this Jesus whom he had persecuted. When the Father sought a Ransomer, a voice like many waters answered, "I will go." Where angels and men were helpless, the Lord of men and angels gave himself to save his people from their sins. He died for those who were still his enemies. He died for Saul of Tarsus. He died for us.

And the man who sees - even faintly - the person and the work of this Jesus, whom God has made both Lord and Christ, asks this: "Lord, what do you want me to do?"

It is a believing sight of Jesus Christ that liberates us from anaemic, self-satisfied, shallow, take-it-or-leave-it religion. Do not say that if only you could see him as Paul saw him, you would have a different attitude. His glory shines on every page of your Bible, and you lack nothing to enable you to truly perceive him. He is the same yesterday, today and forever. He is no less glorious and no less gracious than he was on the day when he appeared to Paul. The Scriptures sing of his majesty and speak of his excellence, painting him in all the glorious colours that God has intended us to see in the portrait of his Son, lit up with the shining light of the Holy Spirit. If we have been given eyes to see and hearts to believe, all that is required is that we love greatly as those greatly forgiven by our great God and Saviour, and live accordingly.

What does it mean? It is not a call to some extravagant but ultimately empty gesture allegedly made for the sake of the kingdom, or some energetic but perhaps pointless demonstration of wrong-headed zeal. It may or may not demand a radical change of direction. It may or may not be a call to a sacrifice of which you have not before dreamed.

But - whatever else it requires - it will demand a change of attitude and call you to a different spirit. It means that you begin to ask not what you must do for Christ, but what you can do. It means a readiness to serve God wherever and whenever he may call us, whether that is where we are now or somewhere else where he would have us to be. It means that we bow the knee before Jesus, God's Lord and Christ, and make a personal, immediate, unconditional, voluntary and active response, asking, "Lord, what do you want me to do?" It means being ready to follow him, whatever the answer, and ready to serve him, whatever the cost. That is a disciple's disposition.

Jeremy Walker is co-pastor of Maidenbower Baptist Church. He blogs at The Wanderer and is co-author of A Portrait of Paul: Identifying A True Minister of Christ (Reformation Heritage Books, 2010).