ISB ~ Mark 1 v40

a leper:Leprosy was a skin disease that made victims unclean, i.e., unfit to participate in the liturgical life of Israel (Lev 13:1-8). Because ritual uncleanness was considered contagious under the Old Covenant—infecting everyone who came in contact with it—lepers were isolated from society to keep those who were clean separated from those who were unclean (Lev 13:45-46). Jesus reaches across this divide when he touches the leper, and though others would be defiled by such contact, he conquers the uncleanness by the greater power of his holiness (1:41; CCC 1503-5). See note on Mt 8:1-9:38.