If God can transform a Saul to a Paul, if God can "appoint to his service" a mean-spirited, blaspheming man of violence like Saul -- what are we waiting for? Why do we think that God probably has not "appointed" us to serve?
Paul freely says that he is a follower of Jesus not because of his upstanding behavior in the past but because of God's mercy and grace. God understands that Paul "acted ignorantly in unbelief" but is now ready to receive God's forgiveness. Ironically, it is Paul's experience with sin and turning away from God that makes him appreciate the gifts of God's mercy and kindness even more.
It was precisely Paul's shameful past behavior that made him an ideal candidate for a future in forgiveness and redemption.
So it is with Paul. He knows he's done some bad things for which he wants God's forgiveness. He knows what it means to "fall short of the glory of God." He has not led a life that has earned God's trust. He has not acted like a disciple, follower or believer of Jesus -- in fact, exactly the opposite is true. Yet Paul is called by God. This is mercy -- to be forgiven not because of any human action but because God chooses to. This is grace -- God's seeing more in Paul than Paul can see in himself. Paul is in a unique position to talk about the value of God's forgiveness and mercy. He has experienced these gifts himself and understands their value in a personal way.
Our past does not have to dictate our future. Because of God's mercy, we are not victims of our résumés. We, like Paul, may have done stuff that's totally contrary to what God wants. God reminds us that our past does not have the final word. The past is prologue.
God will give us the best job ever. The dream job. Not the bed tester, candy taster or island caretaker. God can create something new out of us.
And here's some even better news: Chances are, we won't be asked to travel by boat, donkey or on foot all over the world. We won't be invited to stay inside of prisons. Because, well, that was Paul's job.
But we have been appointed to serve, and it's our job to discover just what is the nature of that service.