124 – Abu Saʿīd (may Allah be pleased with him) reported that the Messenger of Allah (peace and blessings be upon him) said, “Is it not the case that when a woman menstruates she neither prays nor fasts?” Agreed upon, within a longer narration. (1)

Glossary of the ḥadīth
– “Is it not the case that when a woman menstruates she does not pray”: the question here is for affirmation, referring back to the opening of the narration that speaks of a deficiency in a woman’s religious practice.

Lessons derived from the ḥadīth
1 – Prayer is forbidden for a menstruating woman; if she were to perform it, it would be invalid, and she is not required to make up the prayers missed during her period once she attains purity.
2 – Fasting is likewise forbidden for her, but she must make up the number of days she missed while menstruating.
3 – Ibn al-Mundhir, the vizier Ibn Hubayrah, and al-Nawawī said: the scholars are unanimously agreed that a menstruating woman must make up missed fasts, whereas the obligatory prayers of the days of her menstruation are waived. This is based on the report in al-Bukhārī (315) and Muslim (335) in which ʿĀʾishah (may Allah be pleased with her) said, “We were commanded to make up the fast, but we were not commanded to make up the prayer.”
The scholars explained the difference: prayer occurs repeatedly, and requiring its make-up would entail hardship, unlike fasting—and Allah knows best.

Benefit (1)
A menstruating woman is also barred from other acts of worship, such as:
1 – Entering the mosque, in light of the ḥadīth: “I do not permit the mosque for a menstruating woman or for one in a state of major ritual impurity.”