The Centurion's Servant

The Roman army was occupying the land of Israel during the time of Jesus. One of the commanders believed that Jesus could heal his servant. His servant was very sick, paralyzed and close to death. He sent messengers asking Jesus to come to his house. But when Jesus got closer, the centurion sent another message, telling Jesus that he wasn't worthy for Jesus to come. But if Jesus would just say the word, his servant would be healed. How did the centurion know that all Jesus had to do was say it?