Where shall the Imam stand; Mihrab or First Saff
In the name of Allah, the most Beneficent, the most Merciful.
Literally, the Mihrab is used to identify the noblest part of the house, later on it become known as the special section of the Mosque. During the Prophet of Allah Sallallahu Alahi Wasalams time and the rightly guided khulafa’s time is concerned, the custom of making the place where the Imam stands as a separate special unit did not exist. After the early centuries of Islam, the kings promoted this idea. It is in view of the large number of people praying in congregation of a Masjid already short on space that only a place for the Imam to stand is made by going in depth towards the wall facing the Qibla so that full row could be formed behind him. Some scholars have said this practice of reading salah in the Mihrab is a bidah. However, the correct position is that should Mihrabs of this nature to be made for the convenience of the people praying and in the best interests of the Masjids without taking it to be a desired sunnah then there is no reason to call it a bidah.
The Hanafi Jurists have said if the Mihrab is made in the form of a regular place for the Imam to stand and lead the congregation, then it is incumbent on the Imam that he stands slightly outside the Mihrab in a manner that his feet remain out of the Mihrab so that the place in which the Imam and followers are standing can be counted as one. Otherwise, reprehensible and impermissible is the situation in which the imam stands alone in a separate place and the rest of the followers in another. If a Mihrab is so spacious that the imam and muqtadis can fully stand in the Mihrab then becaue of the imam and muqtadis being on common ground the element of detestability will no more be there. (Maariful Qur’an p.274 – p. 275 v. 7)
With regards to your question if the Imam is standing in such a way that his feet is slightly outside the Mihrab then there is nothing wrong with it and there will be no detestability in the Salah. Similarly, if he leads the Salah from the first saff the Salah will be done without any detestability.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham.