Is it permissible to perform the night prayer (Qiyam al-Layl) between the first and second calls to prayer (Adhan), and is continuing to do so an innovation (Bid'ah)?

Performing Qiyam al-Layl (night prayer) at this time—that is, during the last third of the night—is more emphasized and superior because Allah Almighty descends to the lowest heaven during it and says: "Who is calling upon Me that I may answer him? Who is asking Me that I may give him? Who is seeking My forgiveness that I may forgive him?" And it is the closest a servant can be to their Lord. Performing it is the best of night prayers, yet few do it. If one has already prayed their regular wird (portion) of the night, there is no harm in dedicating the time of sahar (pre-dawn) for du'a (supplication) and istighfar (seeking forgiveness), as Allah Almighty says: (And in the pre-dawn hours, they would seek forgiveness.)