Hiding between the seemingly dry—and to the modern ear, somewhat esoteric—laws of Parashat Metzora is a fascinating insight into the nature of reality and human knowledge. The laws of the “plague-afflicted house” and the zav teach us about living in a world where certain things are in principle unmeasurable, and where observation can change reality.
When Avraham is told to leave his country, he’s being told to leave behind more than a mere place. The midrash sees God’s command to Avraham as a lesson in self-transformation. Avram and Sarai cannot give birth to children; Avraham and Sarah will give birth to a nation!