Jesus healed the man’s physical disability. This miracle demonstrated that Jesus had a power that could only have come from God his father. If Jesus only healed the lame, the blind, and the sick, the Jewish leaders may have been satisfied to allow his ministry to continue unmolested. However, Jesus did not come into this world primarily to heal the physically sick; he came into the world to heal the spiritually sick.
Jesus living as human would have been limited to healing people one at a time. Whereas, Jesus as the crucified and resurrected Messiah is lifted up, and everyone who lifts their eyes to him in belief is offered a reconciliation with God, a spiritual new birth, a living relationship with God and eternal life in the presence of Christ for eternity.
Sound Christian living depends upon sound Christian theology, and much of Christian theology involves balancing equally valid truths. Jesus did not come into the world just to bring reconciliation, he also came to bring restoration and transformation. It is a sinful (missing the mark) fallacy to believe that salvation is limited to eternal life. Salvation is intended to transform our lives and our living on earth in the here and the now.
Christ could have limited his offer to the disabled man to spiritual salvation; he did not. Jesus offered him physical restoration. He told him to pick up his mat and walk; his health had been restored. Jesus did not stop there; he sought the man out in the crowd and told him a spiritual truth. Reconciliation and restoration could have been undone if there was not a willingness on the part of the man to experience and live out a transformation. Jesus told him to stop sinning (deliberately disobeying God’s will), for if he did not, he might find himself in a worse condition than he was before he met Jesus.
Salvation comes, in an instant, by faith. Transformation requires time; it results from living in obedience and faithfulness to God.