Jundub bin Sufyaan Radiyallahu 'Anhu relates:
"Once a stone hit the Mubaarak fingers of Rasulullah Sallallahu'Alayhi Wasallam and injured them, they became covered in blood. Rasulullah Sallallahu'Alayhi Wasallam thereupon recited this couplet: 'You are but a finger, no damage has overcome you, besides covering you in blood. This is not fruitless, for reward has been obtained in the path of Allah'".
English reference: Book 36, Hadith 233
Arabic reference: Book 37, Hadith 243