Reference: Sharh 'Umdatil-Fiqh - Tape no.7 q13
Question: If the menstruating woman [completes her menses and] purifies herself after the the time of 'asr has arrived, should she pray the zhuhr and 'Asr prayers, or is she just required to pray the 'Asr prayer?
Response: If she [completes her menses and] purifies herself [even] towards the end of the 'Asr time, then she should combine [the 'Asr] with the Zhuhr; that is because the [legislated] time [period] for the two prayers becomes one time [period] when there is a necessity. So if she [completes her menses and] purifies herself towards the end of the 'Asr time - just before maghrib, so she purifies herself just before Maghrib, then she is required to pray [both] the 'Asr and the Zhuhr [prayers]. [Likewise] if she [completes her menses and] purifies herself before [the time of] fajr [has arrived], then she is required to pray [both] the Maghrib and 'ishaa [prayers].
