The Prophet ﷺ would launch a raid only at the time of the Fajr prayer. If he heard an adhan, he would hold back, and if not, he would attack. One day he listened and heard a man saying, "Allah is the greatest, Allah is the greatest."The Prophet said, "He is upon the fitrah."Then the man said, "I bear witness that there is no god but Allah."The Prophet said, "You have been saved from the Fire."Hasan said, Abu Walid also narrated to us, saying that Hammad bin Salama narrated to us with this chain of transmission the same report.
حدثنا الحسن بن علي الخلال حدثنا عفان حدثنا حماد بن سلمة حدثنا ثابت
كان النبي ﷺ لا يغير إلا عند صلاة الفجر فإن سمع أذانا أمسك وإلا أغار فاستمع ذات يوم فسمع رجلا يقول الله أكبر الله أكبر فقال على الفطرة فقال أشهد أن لا إله إلا الله فقال خرجت من النار قال الحسن وحدثنا أبو الوليد حدثنا حماد بن سلمة بهذا الإسناد مثله
Reference: Also narrated by Muslim, in the Book of Prayer, chapter "Refraining from raiding a people in the land of disbelief when the adhan is heard among them," hadith no. 382, from Hammad bin Salama with the same wording.