"Have you ever gone to an event, a camp, or a sporting event where you paid a fee to get in, and they had a special stamp that marked the back of your hand? The mark is always hard to see, but if at any time during the day you left the event and chose to re-enter, all you had to do was pass your hand beneath a special light and the mark indicating that your admission had been paid would be in clear view. The mark would, of course, enable you to regain admission to the park.
As a baptized Christian, you now bear the mark of Jesus Christ in your life and person. An unbelievable price has been paid for you by Christ on the cross. Now you can understand the solemn exhortation that the apostle Paul gave to his spiritual son when he