بسم الله الرحمن الرحيم
السلام عليكم ورحمة الله وبركاته
Question:
When a menstruating woman becomes pure before before sunrise is it obligatory upon her to perform the maghrib and 'ishaa prayers? Similarly, if she becomes pure before sunset, is it obligatory upon her to perform the dhuhr and 'asr prayer?
Answer:
If a mentruating or post-partum bleeding woman becomes pure before sunset, it is obligatory upon her to perform both dhuhr and 'asr prayers according to the strongest opinion among the scholars. Similar is the case if she becomes pure before dawn. In that case, she must perform the maghrib and 'ishaa prayers. This has been narrated from 'Abdur-Rahmaan ibn Awf and 'Abdullaah ibn Abbaas. This is the opinion of the majority of the Scholars. Similarly, if a menstruating or post-partum bleeding woman becomes pure before sunrise, it is obligatory upon her to perform the Fajr prayer. And from Allaah is guidance.
Shaykh `Abdul-`Azeez Bin Baz From "Islamic Fatawa Regarding Women", Darussalam Publishers and Distributors. P84.