SHOVAVIM TAT (Heb. שׁוׁבָבִים תַּ״ת), an acrostic composed of the initial letters of the names of the first eight weekly sidrot ("Torah portions") of the Book of Exodus which are read in the winter months between *Ḥanukkah and *Purim. Since diseases were prevalent, especially among infants, during the long and hard winter season, it was the custom to recite penitential prayers (*seliḥot) on Thursdays of the weeks in which these portions were read in order to avert disastrous epidemics. These penitential prayers are recited in the morning service in the Ashkenazi ritual, or at the afternoon service only (Italian rite). In many European communities, it was customary to fast on these Thursdays; in others (North Africa) on the Mondays and the Thursdays of the Shovavim Tat period. Penitential prayers and fasting do not take place on Thursdays that coincide with a *Rosh Ḥodesh. Kabbalists (Isaac *Luria, Isaiah ha-Levi *Horowitz), attributed mystical concepts to the observance of Shovavim Tat.
Eisenstein, Dinim, 403–4.