Sahih Bukhari Volume 5, Book 64, Hadith 4108

حَدَّثَنِي أَحْمَدُ بْنُ عُثْمَانَ، حَدَّثَنَا شُرَيْحُ بْنُ مَسْلَمَةَ، قَالَ حَدَّثَنِي إِبْرَاهِيمُ بْنُ يُوسُفَ، قَالَ حَدَّثَنِي أَبِي، عَنْ أَبِي إِسْحَاقَ، قَالَ سَمِعْتُ الْبَرَاءَ، يُحَدِّثُ قَالَ لَمَّا كَانَ يَوْمُ الأَحْزَابِ، وَخَنْدَقَ رَسُولُ اللَّهِ صلى الله عليه وسلم رَأَيْتُهُ يَنْقُلُ مِنْ تُرَابِ الْخَنْدَقِ حَتَّى وَارَى عَنِّي الْغُبَارُ جِلْدَةَ بَطْنِهِ، وَكَانَ كَثِيرَ الشَّعَرِ، فَسَمِعْتُهُ يَرْتَجِزُ بِكَلِمَاتِ ابْنِ رَوَاحَةَ، وَهْوَ يَنْقُلُ مِنَ التُّرَابِ يَقُولُ اللَّهُمَّ لَوْلاَ أَنْتَ مَا اهْتَدَيْنَا وَلاَ تَصَدَّقْنَا وَلاَ صَلَّيْنَا فَأَنْزِلَنْ سَكِينَةً عَلَيْنَا وَثَبِّتِ الأَقْدَامَ إِنْ لاَقَيْنَا إِنَّ الأُلَى قَدْ بَغَوْا عَلَيْنَا وَإِنْ أَرَادُوا فِتْنَةً أَبَيْنَا قَالَ ثُمَّ يَمُدُّ صَوْتَهُ بِآخِرِهَا‏

Narrated By Al-Bara : When it was the day of Al-Ahzab (i.e. the clans) and Allah's Apostle dug the trench, I saw him carrying earth out of the trench till dust made the skin of his abdomen out of my sight and he was a hairy man. I heard him reciting the poetic verses composed by Ibn Rawaha while he was carrying the earth, "O Allah! Without You we would not have been guided, nor would we have given in charity, nor would we have prayed. So, (O Allah), please send Sakina (i.e. calmness) upon us and make our feet firm if we meet the enemy, as they have rebelled against us. And if they intend affliction (i.e. want to frighten us, and fight against us) then we would not (flee but withstand them)." The Prophet would then prolong his voice at the last words.