Tosafos on Shvus De-Shvus and Milah on Shabbos

Full Summary

This shiur examines a complex Tosafos (תוספות) in Bava Basra regarding the permissibility of amira l'akum (instructing a non-Jew) to perform rabbinical prohibitions on Shabbos (שבת). Tosafos distinguishes between different levels of shvus: single shvus is only permitted for yishuv v'yerushah (settling the Land of Israel), while shvus de-shvus (double shvus) is permitted for mitzvos like milah (circumcision). However, Tosafos limits this further, arguing that shvus de-shvus is only permitted for mitzvos that override Shabbos itself, not for other mitzvos like Talmud (תלמוד) Torah (תורה), even though Torah study is considered k'neged kulam (equivalent to all other mitzvos). The shiur raises a fundamental question about Tosafos's reasoning. If the principle were simply about the importance of mitzvos (as the Rambam (רמב"ם) suggests with 'tzorech mitzvah (מצוה)'), then Torah study should certainly qualify. Instead, Tosafos appears to be establishing a principle of dechiyah (overriding) - that only mitzvos which override Shabbos at the Torah level can override rabbinical Shabbos prohibitions. A key difficulty emerges: if this is truly about dechiyah, why can a mitzvah that overrides Shabbos not override a single shvus, but can override a double shvus? The analysis suggests that Tosafos distinguishes between two types of rabbinical prohibitions. Single shvus represents a lo ta'aseh (negative commandment) - prohibitions designed to prevent one from coming to perform actual melakha. Double shvus, however, represents an aseh (positive commandment) - obligations designed to maintain the sanctity and importance of Shabbos (shelo yihyeh Shabbos kalah b'einecha). This distinction is crucial for understanding the laws of dechiyah. An aseh overrides a lo ta'aseh only when performed simultaneously (b'idna), but an aseh can override another aseh even when not simultaneous, provided the overriding mitzvah is more important. Since actions involving single shvus (like warming water) are always performed before the mitzvah (like milah), they cannot qualify for dechiyah. However, shvus de-shvus, being classified as an aseh, can be overridden by a more important mitzvah even when not performed simultaneously. Tosafos's final limitation - that only mitzvos which override Shabbos can utilize this principle - stems from his understanding that the mitzvah must be inherently capable of overriding Shabbos-level prohibitions to justify overriding even rabbinical Shabbos enactments.