Purity: Divorce During Menstruation (Ḥayḍ)
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 452:
As per the laws relating to divorce, divorcing a woman who is in the state of ḥayḍ is invalid.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)


