Musannaf Ibn Abi Shayba 36:278

Abu al-Ahwas narrated to us, from Abu Ishaq, from al-Bara’, who said: I saw the Messenger of Allah (may Allah bless him and grant him peace) on the day of the Trench carrying dirt until the dirt covered the hair of his chest. He was reciting the rajaz poetry of Abdullah ibn Rawahah, saying: "O Allah, were it not for You, we would not have been guided, nor would we have given charity, nor would we have prayed. So send down tranquility upon us, and make firm the feet if we meet [the enemy]. Indeed, those [people] have transgressed against us, and if they intend sedition, we refuse."