When a menstruating woman achieves purity (Tuhur) just before the time for the next prayer begins, which prayers become obligatory?
Chapter on Prayer Times
Al-Mughni
Book of Prayer
Primary text
If a woman becomes pure before the time for the next prayer begins—such as purifying before sunset, before dawn, or before Dhuhr—she is obligated to pray both the preceding prayer and the current prayer. This view is held by scholars including Abd al-Rahman ibn Awf, Ibn Abbas, Tawus, Mujahid, Al-Nakha'i, Al-Zuhri, Rabi'ah, Malik, Al-Layth, Al-Shafi'i, Ishaq, and Abu Thawr. The basis for this is the report from Abd al-Rahman ibn Awf and Abdullah ibn Abbas: if a menstruating woman becomes pure one rak'ah time before dawn, she prays Maghrib and Isha; if pure before sunset, she prays Dhuhr and Asr together. This is because the time of the second prayer serves as the time for the first prayer during the state of excuse (excused state), so when the excused person attains that time, the obligation of the preceding prayer becomes binding, just as the obligation of the second prayer becomes binding.
Supporting text
A different opinion, attributed to Al-Thawri and the Ashab al-Ra'y, is that only the prayer whose time she attains purity within is obligatory. This is based on the principle that the time for the first prayer expired during her excused state, thus making it not obligatory, similar to a person who does not catch any part of the chosen time for the second prayer. Imam Ahmad stated that most of the Tabi'in followed this view, except for Al-Hasan alone who held this position. Additionally, a view attributed to Malik states that if the woman catches the time equivalent to five rak'ahs of the second prayer, the first prayer becomes obligatory. This is because the time for the first rak'ah of the five is considered the time for the first prayer during her excused state, thus being necessitated by reaching that duration, unlike when she catches less than that amount.