Traces the development of bal tashit the Jewish prohibition against wastefulness and destruction from its biblical origins to the contemporary environmental movement.Winner of the 2020 Canadian Jewish Literary Award in the category of Jewish Thought and CultureBal tashit the Jewish prohibition against wastefulness and destruction is considered to be an ecological ethical principle by contemporary Jewish environmentalists. Waste Not provides a comprehensive intellectual history of this concept charting its evolution from the Bible through classical rabbinic literature commentaries codes of law responsa and the works of modern environmentalists. Tanhum S. Yoreh uses the methodology of tradition histories to identify pivotal moments in the development of the prohibitionin particular its transition into an economic framework. He finds that bal tashits earliest stages of conceptualization connect the prohibition against wastefulness with avoidance of selfharm. This connection is commonplace within contemporary environmental thought and a universalizing Jewish principle with important contributions to be made to Jewish and general societal ecological discourse. This narrative provides a foundation for understanding bal tashit as an environmental ethic for today and tomorrow.