Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Noble Prophet (peace and blessings of Allah be upon him) said: "When the call to prayer (adhan) is given, the gates of the heavens are opened and supplication is accepted."

Makhool says that the Prophet Muhammad (peace be upon him) said: "Seek the acceptance of supplication at the time when (the armies of Islam and disbelief) are clashing on the battlefield, when the call to establish prayer (iqamah) is being made, and when rain is falling."

Sayyiduna Amr bin Abasah (may Allah be pleased with him) narrates that the Noble Prophet (peace and blessings be upon him) said: "The night prayer is in sets of two rak‘ahs, and in the last part of the night, supplication is most readily accepted." I asked: Is it obligatory to supplicate in that part? He (peace and blessings be upon him) said: "No, no, (I am saying that) supplication is most readily accepted."