At least five significant changes occur in the men in Mark 5:15 and Luke 8:35:
First, the exorcism left the men with a new posture, that of sitting and resting, in direct contrast to the constant roaming and wandering about the tombs and mountains and wilderness day and night. Christ says in Matthew 11:28, "Come to me, all you that labor and are heavy burdened, and I will give you rest." A problem of sin is discontentment, the lack of peace and rest (Isaiah 57:20-21). However, that all changed when Christ entered the lives of the demon-possessed men to deliver them from the evil adversary.
Second, before the exorcism, the possessed men want nothing to do with Christ, but afterward a tremendous change in attitude occurs: The delivered men want to go with Christ out of reverence and respect for their "Savior." Jesus, though, has something else in mind: It is more important that they witness to others of what happened. Jesus instructs His disciples, "If anyone desires to come after Me, let him deny himself, and take up his cross daily, and follow Me" (Luke 9:23). A man may want to follow Jesus physically, but Jesus wants him to take up his cause for Him.
Third, before their deliverance they wear no clothes, yet afterwards they are clothed (Luke 8:27, 35). Sin makes people shameless and immodest, a natural development due to their separation from the righteous God. The men's spiritual cleanness is indicated by visible changes; modesty, cleanliness, and appearance improve, as it does when anyone is delivered by Christ. Wherever God's truth is received, people's morals improve, reflected in modest clothing.
Fourth, they regain their sanity. Fools, not wise men, reject God (Psalm 14:1), and sin invites Satan into a person's mind. Ultimately, his influence causes madness. Jesus explains: "When an unclean spirit goes out of a man, he goes through dry places, seeking rest; and finding none, he says, 'I will return to my house from which I came.' And when he comes, he finds it swept and put in order" (Luke 11:24-25). When a demon is removed, a person's mind is cleaned of chaos and made orderly. To avoid being possessed again, he needs to replace what was swept out with God's Spirit and truth.
Fifth, the words "right mind" (Mark 5:15; Luke 8:35) suggest the controlling of thoughts and actions, so it indicates, not only sanity, but also self-control. The demons in the men are uncontrollable ("neither could anyone tame him," Mark 5:4), but when Jesus comes, they recognize God's authority over them. Evil people cannot control their desires, and society cannot control them, so crime rages on. Living God's way of life as revealed in the life of Christ is the answer. God provides the right mind to produce the fruit of the Spirit, including self-control (Galatians 5:23).
Jesus instructs the healed man to tell people about his deliverance, particularly those who were familiar and intimate with him. He wants him to be an example of God's grace, first among his own family and friends, so that they can come to repentance. A Christian is first responsible for witnessing to those closest to him, who will see the greatest difference in him as he lives God's way of life.
Martin G. Collins
The Miracles of Jesus Christ: Two Demon-Possessed Men Healed (Part Three)