ذِكْرُ الْبَيَانِ بِأَنَّ الْأَذَانَ إِذَا سُمِعَ فِيَ مَوْضِعٍ مِنْ دُورِ الْحَرْبِ حَرُمَ قِتَالُهُمْ
That the Prophet ﷺ would not attack except near the time of Fajr, so if he heard the Adhan he would refrain, and if not, then he would attack. So he listened one day and heard a man saying: "Allahu Akbar, Allahu Akbar," so he said: "Upon the Fitrah." Then he said: "I bear witness that none has the right to be worshipped but Allah." So he said: "You have departed from the Fire." (Using translation from Tirmidhī 1618)
أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يُغِيرُ عِنْدَ صَلَاةِ الصُّبْحِ فَيَتَسَمَّعُ فَإِنْ سَمِعَ أَذَانًا أَمْسَكَ وَإِلَّا أَغَارَ قَالَ فَاسْتَمَعَ ذَاتَ يَوْمٍ فَإِذَا رَجُلٌ يَقُولُ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ فَقَالَ «الْفِطْرَةُ» فَقَالَ أَشْهَدُ أَنَّ لَا إِلَهَ إِلَّا اللَّهُ فَقَالَ «خَرَجَ مِنَ النَّارِ»