Muhammad bin al-Munkdar bin 'Abdullah محمد بن المنكدر بن عبد الله بن الهدير · The Book on Military Expeditions

"Abdul-Warith bin Sa'eed narrated to us from 'Urwah bin Thabit, from Az-Zuhri." This Hadith is Hasan Gharib.

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."