Fast - menstruation

God hath exempted women who are in their courses from obligatory prayer and fasting. Let them, instead, after performance of their ablutions, give praise unto God, repeating ninety-five times between the noon of one day and the next 'Glorified be God, the Lord of Splendour and Beauty'. Thus hath it been decreed in the Book, if ye be of them that comprehend.

Bahá’u’lláh, Kitáb-i-Aqdas, p. 23