In Mark 5, a man named Legion who had an unclean spirit was living in some tombs and all day and night he would cry out and cut himself with stones. He was too strong to be locked with shackles and chains, that is, until he had an encounter with the Son of God.
Jesus said, "Come out of the man, unclean Spirit!" Then the demons begged to enter into some swine, so Jesus permitted it. Nearby people were amazed to see this once demon-possessed man sitting next to Jesus and being clothed.
The point of this is that Jesus has done the same for us. He has made us a new creation and clothed us with his righteousness. People can now look at us and be astonished that we can now sit next to Christ and be clothed. I am not saying that we were once all demon-possessed, but we were all slaves to sin. This man who was freed from being demon-possessed asked to go with Jesus as he left, but Jesus said, "Go home to your friends, and tell them what great things the Lord has done for you, and how He has had compassion on you" (v.19).
We get to do the same: tell other people (friends) what great things the Lord has done for us, and how He has had compassion on us. We have the opportunity to do this because just as the demon-possessed man was set free from the unclean spirits, we have been set free from sin.