Fatimah bint Yahya (rah) was a great Mujtahidah of the 9th Century. A Mujtahidah (which is the feminine version for the term 'Mujtahid') is a scholar of great calibre who can deduce from the sources of Islamic law. In turn they use these deductions to give rulings in accord with both the contemporary and individual needs of the society. For one to be given the title ‘Mujtahidah’, one must have knowledge on both the consensus and opposing views of the Companions, the Successors, and the leading Scholars of Fiqh and Mujtahidoon. Hence, to be a Mujtahidah was not small matter, but Fatimah bint Yahya (rah) truly deserved it.
Such was her knowledge, that her father – who was also a great jurist with several students – would be questioned by Fatimah (rah) regarding several Juristic issues. The great scholar Al Shawkani (rah) says about her:
‘She was most famous for her knowledge. She had debates with her father on several juristic issues. Her father, the imam, confirmed that Fatimah applied ijtihaad in deriving rulings. This indicates that she was prominent in the knowledge for the imam would not say something like that except for one who deserved it.’
Her father married her to the scholar al-Mutahhar ibn Muhammad ibn Sulaymaan ibn Muhammad (d. 879). Al-Mutahhar (rah) was very lucky since whenever he would be confused on a matter he would refer to his wife for judgement on difficult juristic issues. Even within the midst of his students, when he would get stuck on a complicated issue, he would get up and head for the curtain, behind which the great Mujtahidah would be sitting.
When he would come back with the answer his students would say,
‘This is not from you. This is from behind the curtain.’
Source: Muslim Women Who Taught Their Husbands