Sayyiduna Abu Hurairah (may Allah be pleased with him) saw a man leaving the mosque after the adhan and said: He has disobeyed Abu al-Qasim (peace and blessings of Allah be upon him).
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1239
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده صحيح وأبو الشعثاء هو: سليم بن الأسود، [مكتبه الشامله نمبر: 1241]
That is, to leave the mosque after giving the adhan (call to prayer) without a valid Shar‘i (Islamic legal) excuse is an act of disobedience to the Messenger of Allah (sallallahu alayhi wa sallam), and this action is reprehensible (makruh).