Sayyiduna Anas (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) would attack at dawn; if he heard the call to prayer (adhan), he would hold back, otherwise he would attack.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18236
Sayyiduna Anas bin Malik (may Allah be pleased with him) said: When the Messenger of Allah (peace and blessings be upon him) fought a people, he would not attack before morning. If he heard the call to prayer (adhan), he would refrain from attacking, and if he did not hear the call to prayer, he would attack after morning had come.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18237
Ibn Isam narrates from his father (may Allah be pleased with him) that whenever the Prophet (peace and blessings be upon him) sent out a small detachment, he would say: "If you hear a caller to prayer or see a mosque, do not kill anyone."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18238