Answered by Sidi Fadi Qutub Zada
I read on the Shafii Fiqh List that (outside of a masjid) if a follower in salah cannot see the imam or cannot see a follower who can see the imam, then that followers salah is invalid. Is this the same for Hanafis? As the practice at our university is to allow sisters for Jummah behind a purdah, whereby they can hear the imam but not see him nor see anyone who can see the Imam.
The great hanafi jurist Imam al-Tumurtashi says in his book Tanweer al-Absar, along with Imam al-Haskafi in his commentary on this text the following:
And a barrier does not prevent (the following of the imam) if the condition of ones imam is not unclear (by hearing or by seeing)
The greatest hanafi imam of his time, Ibn Abidin, comments on Imam al-Haskafis words:
(His saying: by hearing) that is, from the imam or from a follower raising his voice with the takbeers (f: i.e. saying Allahu akbar in the transitions). (His saying: or by seeing) it is all the same whether one sees the transitions of the imam or one of the followers.
[Hashiyat Ibn Abidin 1:394]
The upshot is that if the state of the imam is clear to the sisters by merely hearing him, or hearing the mukabbir (follower who raises his voice with the takbeers), then their prayer is correct and valid.
[Faraz: The scholars mention that there are 2 conditions for ones following the imam to be valid: a) one must be in the same place (actually or effectively); b) one must know about the movements of the imam (directly or indirectly). It is valid to follow based on loudspeaker or a monitor if one is doing so from the same place.]
And Allah alone gives success