Is it obligatory to perform ghusl (ritual bathing) again, or just to shower, if a single drop of blood is discharged after performing ghusl following masturbation on the sixth day of menstruation?

Scholars differ on whether a drop of blood is considered menstruation. The majority of scholars hold that it is not menstruation, while the Malikis consider it to be menstruation.

However, the Malikis do not consider ghusl (ritual bath) obligatory for it if it appears after purification from menstruation or postpartum bleeding; rather, only wudu (ablution) is required.

So, if ghusl was performed after purification, then only wudu is obligatory. But if it was performed before the completion of purification, then the ghusl is invalid and must be repeated.