[Leprosy] was a feared disease, and its victims were shunned because of their disfiguring stigmata—collapsed facial bones, fingers, and toes, with the hands and feet ultimately rotted away. Leprosy was among the first diseases identified as contagious. Early societies took measures to shield their healthy members from contagion: lepers were obliged to wear distinctive clothing and carry a bell to warn others of their presence, or they were segregated in lazarettos, precursors of quarantine stations and isolation hospitals. (source)
We are given the impression that perhaps Jesus is alone in the wilderness on the outskirts of a town or city. He was probably praying and escaping the pressure of His growing fame. Jesus seeks the refuge of the wild for peace and the leper seeks it for peace as well but for different reasons. Here we see Jesus associating with the most marginalized of His time, lepers. We may assume He is alone, otherwise word of this "touch" would have spread just as fast if not faster than word of His miracles (we know how fast bad news travels). With a word and a touch Jesus cleanses this man thus removing the social and physical pains associated with his disease in an instant.
Jesus instructs this man to keep quiet but the man cannot help himself. I doubt that Jesus was too upset with this man for not following His wishes. Yet, He may have been disappointed for the news of the cure made it more difficult for Him to travel from town to town.
A few lessons might be taken from this passage that we can apply to our own lives. There are many diseases today that cause man to be marginalized. Yet, again, we must be concerned with the one disease that truly is a silent killer, leprosy of the soul, sin. This disease disfigures a being created in the image and likeness of God beyond recognition (depart from me, I do not know thee.) It is a slow rotting of the soul. Our goal should be to seek Christ often, finding Him in the silence, peace and wilderness of the confessional. We should seek to often enter into that place and cry out from the heart, "If you will, you can make me clean." There we will hear, "I do will, be made clean."
In addition, being faithful in little commands can further the kingdom while disobedience can often act in opposition to God's grace. How much more difficult is it for Christ to speak and heal when we are the ones speaking. People who knew the leper did not need to hear the story of his healing, they need only look at him for proof. So it is with us. We need not run from person to person telling them about all the Lord has done, let them see the fruits of the healing in the way we live our lives. They will notice the leprosy of our souls has been healed.
FROM THE SAINTS - "This man prostrated himself on the ground, as sign of humility and shame, to teach each of us to be ashamed of the stains of our life. But shame should not prevent us from confessing: the leper showed his wound and begged for healing. If you will, he says, you can make me clean: that is, he recognized that the Lord had the power to cure him." - Saint Bede