Is one who vowed to study medicine then turned away from it considered a breaker of their vow, based on the opinion of some jurists—especially the Shafi‘is—that a vow includes communal obligations (Fard Kifayah)?

Scholars have stated that learning medicine is a communal obligation (fard kifayah). Vowing to perform an obligatory act (whether individual or communal) is not binding according to the majority of jurists, such as the Hanafis, Malikis, and Hanbalis, because it is an act of "gaining what is already gained" (tahsil hasil), and there is no obligation to fulfill it. However, the Shafi'is hold that a communal obligation becomes binding by a vow, especially if it is among the acts of devotion. As for permissible acts, the majority also agrees that there is no obligation to fulfill a vow concerning them. Therefore, vowing to learn medicine is not binding according to the majority of jurists. Nevertheless, whoever makes such a vow and is unable to fulfill it should offer an expiation for breaking an oath (kaffarat yamin) to avoid disagreement.