A Positive Commandment Overrides a Negative One: The Tannaitic Source of this Principle and its History

That a positive commandment overrides a negative one is one of the best known fundamental principles in the Talmud. It means that when the fulfillment of a positive commandment clashes with the observance of a negative one, the discharging of the positive one takes precedence. This article examines the source and history of this principle in Tannaitic and Ammoraic literature. Within the entirety of the Tannaitic literature this rule appears only twice, both times in the Mekhilta de-Rabbi Yishmael, and it apparently was not accepted as a comprehensive principle by all the Tannaim. In the matter of the obligation to attach zizith (fringes) to a sheet, the Mekhilta to Deuteronomy attributed this principle to both the Academies of Shammai and Hillel. However, this was apparently a later explication for their original controversy which really dealt with an entirely different issue. There is no mention of this principle in the Mishnah. There is a difference of opinion between the Mekhilta and the Mishnah in Bava Mezia concerning the conflict between the obligation to return a lost object and a priest's obligation to avoid defiling himself in order to return it. The Mekhilta justifies its position by the principle that `a positive commandment overrides a negative one' while the Mishnah implicitly does not accept this principle. Indeed, in the fourth generation of Ammoraim in the Land of Israel, R. Yossi continues to advocate the Mishnah's position by asserting that 'a positive commandment overrides a negative one' only when the two biblical verses containing the positive and negative commandments are adjacent to each other. However, in the case of any other negative commandment clashing with a positive one, there is no preference for the positive commandment over the negative one. However, the Babylonian Talmud testifies that Reish Lakish, a second generation Ammorah in the Land of Israel, adopts the Mekhilta's principle: 'Any place where you find positive and negative commandments and you can fulfill both of them, fine; and if not, the positive commandment overrides the negative one'. In the fourth generation of Babylonian Ammoraim, Rava adopted Reish Lakish's rule, and was involved in litigation based upon it and developing it. Thereupon, this principle became the general convention and consensus in Babylonia, and diverse and intensive deliberations concerning it have continued throughout the entire course of rabbinic literature. Towards the end, this essay also discusses the conceptual implications of the conflict between the active fulfillment of a positive commandment and the passive observance of a negative one.