As the Torah continues its discussion of spiritual "leprosy," we learn that this strange malady can affect not only one's person, but also his clothing and his home. Though the laws in the Torah are taught in that order - person - clothing - home, rabbinic tradition teaches that the outbreak would take place in inverse order: First the home would be afflicted, then the clothing, and finally the person him- or herself. The sequence is significant; it progresses from impersonal to personal, giving the sufferer various opportunities to discern the spiritual message and resolve to make amends.
Regarding the affliction of a house, the Torah prefaces the law with the qualification that it will apply "when you come to the land of Canaan." (Lev. 14:34) Recognizing, as we do, that the malady in question is a physical manifestation of a spiritual ailment, we are not surprised that the law will apply only in the Land of Israel, where the nation will be expected to live a more exalted moral and spiritual existence. What is surprising is that in this particular context, the Promised Land is referred to as "the land of Canaan." There is certainly no dearth of possibilities when referring to the Land of Israel; the Israelites' ultimate destination is variously referred to as the land promised to the patriarchs, or the land flowing with milk and honey, or even the land presently controlled by various other tribes. Why, specifically regarding the affliction of a home with tzara'at, does the Torah single out Canaan?
Rabbinic tradition addressed the laws regarding "leprosy" through the prism of spirituality, noting the connection between tzara'at and tzarut 'ayin (stinginess or miserliness of spirit). In particular, we are taught that a person who turns down a neighbor's request to borrow a tool or utensil, claiming that he does not own the item in question simply because he does not wish to share, will be struck with tzara'at. The prescribed treatment for tzara'at that afflicts a house, outlined in Parashat Metzora, is to cast the contents of the leprous home out of doors, effectively placing all the miser's possessions on public display for all the rebuffed neighbors, relatives and friends to see.
And yet, the question remains: How does this relate to Canaan?
After the flood, Noah, ostensibly suffering from post-traumatic stress and perhaps some guilt for having survived while saving nary a soul, becomes intoxicated. His son Ham finds him lying naked and drunk on the floor, and seizes the opportunity to abuse his father. Noah's two remaining sons see this and respectfully cover their father while averting their eyes from his embarrassment.
When Noah awakens from his alcohol-induced slumber and realizes what his son has done, his response is strange. Rather than responding to the outrage or disciplining Ham, Noah makes a very harsh pronouncement regarding Ham's son, Canaan. Apparently, this is not as much a curse as a statement of cause and effect: The son who showed no respect for his father will in turn know disrespect from his own son.
Honoring one's parents is the most basic and logical of interpersonal laws, and its "spill-over" effects are far-reaching: The son who respects his parents will, by extension, be kind to his siblings and their children as well. It is not difficult to see how this affects the dynamics of the entire Jewish People: We are one family, one fraternity; we are all brothers and sisters, hence our homes should be open to our neighbors, and our good fortune shared with a glad heart and spirit. This is what sets us apart from the descendants of Ham and his son Canaan, and it is this understanding of our familial responsibilities that causes the land occupied by Canaan to be given to the children of Shem through the line of Avraham: Only when we create a charitable and kind society, a society based on mutual responsibility, a society based on our sense of family, will we merit this inheritance. To behave like Ham or like Canaan, to turn our backs on our brothers and sisters, to be motivated by tzarut 'ayin rather than the hesed that is the hallmark of Avraham and Sarah's descendants, is an affront to the values of our forebears and to God Himself, as well as to the Land of Israel.
For a more in-depth analysis see: http://arikahn.blogspot.co.il/2014/03/audio-and-essays-parashat-metzora.html