A flavour of the midrashic tradition and an appreciation of its width and depth can be gained from Samuel Rapaport's Tales and Maxims from the Midrash (be warned though, it is very old - published in 1908). An online edition can be accessed by clicking here.
Alternatively for a contemporary view, click here for Daily Halakha
Early Christian writing on Mark 1:40-45
Origen (c185 - c245)
And why did [Jesus] touch [the leper], since the law forbade the touching of a leper? He touched him to show that "all things are clean to the clean." ...So, stretching forth his hand to touch, the leprosy immediately departs. The hand of the Lord is found to have touched not a leper, but a body made clean! Let us consider here, beloved, if there be anyone here that has the taint of leprosy in his soul, or the contamination of guilt in his heart? If he has, instantly adoring God, let him say: "Lord, if you will, you can make me clean."
The Healing of the Leper
[Jesus] did not simply say, "I will, be cleansed, "but he also "extended his hand, and touched him" - an act we do well to analyse. If he cleansed him merely by willing it and speaking it, why did he also add the touch of his hand? For no other reason, it seems to me, than that he might signify by this that he is not under the law, but the law is in his hands. ... He touched the leper to signify that he heals not as a servant but as Lord. For the leprosy did not defile his hand, but his holy hand cleansed the leprous body.
Gospel of St Matthew, Homily 25.2
In the performance of this miracle Jesus requested silence. Yet it did not remain concealed in silence for long. So it is with the called people of God - while following his precepts and example, they may prefer their responsible actions to remain unspoken, yet for the benefit of others providence may allow them to become known contrary to their own wishes.
Homilies on the Gospels 1.10