During the time of a woman's period she is allowed not to read the namaz and the namaz of that time she has not to read later too. But If a woman leaves a fasting during her periods, she has to fast the left ones after the RAMAZAN. Now why is it when the namaz is more important than fasting?
In the book علل الشرائع (reasons of the rulings) by Shaikh Saduq. To get a better understanding of what the book is about, I've mentioned a few chapters
- reasons for Naming Prophet Nuh, Nuh (and many other names)
- reasons for the necessity of wudu
- reasons for why a woman during pregnancy does not bleed.
- reasons for why a stone grave is made rectangular.
specifically there's a chapter named:
العلة التي من اجلها تقضى الحائض الصوم ولا تقضى الصلاة
The reasons why a women has to do the qadaa for her fastings but doesn't do qadaa for her prayers.
عن ابی بصیر، قال:سالت الا عبد الله (ع) ما بال الحائض تقضی الصوم و لا تقضی الصلاه؟
قال: لان الصوم انما هو فی السنه شهر،و الصلاه فی کل یوم ولیله، فاوجب الله علیها قضاء الصوم و لم یوجب علیها قضاء الصلاه لذلک
Abi Basir ask Imam Sadiq (PBUH): Why should a women do the Qadaa for her fasting but not do it for her prayers?
Imam Sadiq replied: Because fasting is just a single month of the year, but prayer is every day. Because of this (to reduce the burden on her) doing the qadaa for the fasting is wajib, while he has not made doing qadaa for prayers wajib.