In this case, she treats the blood that bears the marks of menstruation as actual menses: she ceases praying and fasting for its duration. All other bleeding is deemed istihādah. When the blood with menstrual characteristics stops, she performs a full ritual bath, then resumes prayer and fasting and is considered ritually pure. This is based on the Prophet’s ﷺ words to Fāṭimah bint Abī Ḥubaysh: “When it is menstrual blood—it is dark and recognizable—refrain from prayer; but when it is the other type, perform ablution and pray.” Reported by Abū Dāwūd and al-Nasāʾī, and declared sound by Ibn Ḥibbān and al-Ḥākim. The ḥadith establishes that a woman experiencing istihādah relies on the appearance of the blood to distinguish between menses and other bleeding.

The third situation: If she has neither a known habit nor blood whose color or qualities distinguish it, she assumes the common length of menstruation—six or seven days each month—because that is the pattern of most women. The proof is the Prophet’s ﷺ instruction to Ḥamnah bint Jahsh: “It is only a kick from Satan. Menstruate for six days or seven, then bathe; once you are clean, pray for twenty-four days or twenty-three, and observe your fasting and prayer. That will suffice you. Do likewise as other women menstruate.” Narrated by the five compilers and graded sound by al-Tirmidhī.