In this daily Bible reading is the account of Jesus encountering a violent demon-possessed man on the east side of the Sea of Galilee. The man was possessed with many demons and could not be controlled. When the man saw Jesus, he fell down before Jesus, acknowledging Jesus to be the Son of God. Jesus commanded the demons to come out of the man. The demons implored Jesus to send them into a herd of swine that was nearby. Jesus did so. The swine stampeded into the sea and were drowned.
The demon–possessed man was then in his right mind. He asked Jesus to take him along with Jesus. However, Jesus told him to go to his village and tell the people what Jesus had done for him. The man would be a very credible witness to what Jesus could do, as everybody knew of the demon-possessed man.
As believers, Jesus does many good things for us. Good things happen in our lives that can only be explained by acknowledging that God provided the blessings for us. We are therefore witnesses to the good that God does and how He provides for us. We cannot and should not lecture others on how to live their lives, but we can share a personal experience that will glorify God. That is what it means to witness.