From: Fatāwā ʿUlamāʾ-e-Ḥadīth, Kitāb al-Ṣalāh, Volume 1, Page 158
(Qawānīn-e-Fiṭrat, Volume 7, Issue 5)
❀ Question
While giving the adhān (call to prayer), should one insert fingers into both ears, or is it permissible to insert a finger into one ear and leave the other ear open?❀ Answer
It is recommended to insert fingers into both ears while giving the adhān. There is no Sharʿī evidence supporting the practice of inserting a finger into only one ear while leaving the other open. A person doing so might simply be following a local custom, for which Islam provides no basis.(Qawānīn-e-Fiṭrat, Volume 7, Issue 5)