Mishnah Shevuot 2:2 describes (or constructs) a processional ritual for expanding the Temple’s temenos. It includes a non-descript “song” (shir). In commenting on this part of the ritual, Bavli Sheuvot 15b presents a baraita that lists the contents of this shir, which includes numerous psalms and a liturgical unit called the shir shel pegaim. The stam (and a late amora in a somewhat parallel passage in Yerushlami Shabbat) identifies this unit as Psalm 91. Based on this identification, modern scholars have typically assumed that Psalm 91 was already understood by this moniker in the Second Temple period. Such is possible. But it reads history backward. I argue that it is more historically plausible that shir shel pegaim referred to an exorcism poem that continued to circulate in the late ancient period. The baraita and its Yerushalmi parallel preserve mention of such a work. Magical texts live long lives. The localization of shir shel pegaim as Psalm 91 (and possibly also Psalm 3), I argue, belongs to a larger rabbinic reading strategy, a canon-bound consciousness that narrowed most pre-rabbinic sources of authority to the Bible alone.
