Must someone who vowed to fast three days if he committed a sin, and he committed it out of forgetfulness and remembered his vow after committing it, make up the fast?

The aforementioned vow is one of a "Lajaj" (insistent) and anger-induced vow. Scholars have differed regarding one who breaks such a vow out of forgetfulness. The Hanafis and Malikis hold that forgetfulness necessitates breaking the vow, while the Shafi'is believe it does not break it at all. The Hanbalis, however, maintain that it does not break the vow except in cases of divorce and manumission. It is more prudent to fulfill the vow or offer expiation for the oath to avoid scholarly disagreement.