Sahih al-Bukhari 6146
Narrated Jundub:
While the Prophet (ﷺ) was walking, a stone hit his foot and stumbled and his toe was injured. He then 
(quoting a poetic verse) said, "You are not more than a toe which has been bathed in blood in Allah's 
Cause."
حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا سُفْيَانُ، عَنِ الأَسْوَدِ بْنِ قَيْسٍ، سَمِعْتُ جُنْدَبًا، يَقُولُ بَيْنَمَا النَّبِيُّ صلى الله عليه وسلم يَمْشِي إِذْ أَصَابَهُ حَجَرٌ فَعَثَرَ فَدَمِيَتْ إِصْبَعُهُ فَقَالَ ‏
"‏ هَلْ أَنْتِ إِلاَّ إِصْبَعٌ دَمِيتِ وَفِي سَبِيلِ اللَّهِ مَا لَقِيتِ ‏"‏‏.‏