Two supplications are never rejected, or are rarely rejected: supplication made upon hearing the call to prayer and during battle when the two armies are engaged in fighting
Sahl ibn Sa‘d (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "Two supplications are never rejected, or are rarely rejected: supplication made upon hearing the call to prayer and during battle when the two armies are engaged in fighting.”
Reported by Abu Dawud (No. 2540) and Ad-Darimi (No. 1174).
This Hadīth clarifies the virtue of Jihad, as Allah, the Exalted, answers the supplication of the Mujāhid when he is engaged in the battle. It also clarifies the virtue of the call to prayer as Allah, the Exalted, answers the supplication of the Muslim when the Adhān is announced and until the Iqāmah is announced.
Explanation in Arabic
في هذا الحديث بيان فضل الجهاد في سبيل الله حيث يستجيب الله تعالى لدعاء المجاهد وهو في المعركة، وفيه أيضاً بيان فضل الأذان حيث يستجيب الله تعالى لدعاء المسلم عند الأذان وحتى إقامة الصلاة.
استحباب الدعاء في هذين الوقتين لما لهما من فضيلة الإجابة.
أنَّ الدعاء من أقوى الأسباب في دفع المكروه وحصول المطلوب.