What is the rationale for setting the Istibra' period for potential pregnancy at three months?
General Chapter
Al-Mughni
Book of Waiting Periods ('Iddah)
Primary text
The duration of three months is established because pregnancy is not detectable earlier. 'Umar ibn 'Abd al-'Aziz gathered scholars and midwives who unanimously agreed that pregnancy is not manifest in less than three months. Ahmad further supported this by citing Ibn Mas'ud's description of fetal development: forty days for the drop of fluid (nuṭfah), followed by forty days as a clinging mass ('alaqah), and then a chewed lump (muḍghah). Once eighty days pass, the fetus becomes recognizable as flesh (muḍghah), making detection possible.
Supporting text
The justification for substituting one month for one menses in cases where menstruation is absent is derived by analogy with the waiting period for a woman whose menstruation has ceased (the *ā'isah*), where the waiting period is three months replacing three cycles. For a female slave whose menstruation is absent, the waiting period is ten months: nine for pregnancy and one month replacing the menses.