Al-Matalib al-'Aliyah 4274 — The Battle of the Confederates

It is narrated from Abu Uthman al-Nahdi (may Allah have mercy on him) that during the Battle of the Trench (al-Khandaq) the Messenger of Allah (peace and blessings be upon him) struck (the ground) with both his blessed hands and then said: "'Bismillahi wa bihi badayna, wa law 'abadna ghayrahu shaqayna, habbadha rabban wa habbadha dinan' (In the name of Allah, and by His help we have begun our work; and had we worshipped any other than Him we would surely have been wretched and ruined; how excellent a Lord He is, and how excellent a religion this is!)"
Imam al-Harith bin Abi Usamah narrated this in his Musnad, and all its narrators are thiqat (trustworthy).