Sahih Muslim , Book 19, Hadith 4426 (USC-MSA) ⓘ
It has been narrated on the authority of Jundub b. Sufyan who said: A finger of the Messenger of Allah was wounded in one of the encounters He said: Thou art just a little finger which has bled, and what thou hast experienced is in the cause of Allah.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، وَقُتَيْبَةُ بْنُ سَعِيدٍ، كِلاَهُمَا عَنْ أَبِي عَوَانَةَ، قَالَ يَحْيَى أَخْبَرَنَا أَبُو عَوَانَةَ، عَنِ الأَسْوَدِ بْنِ قَيْسٍ، عَنْ جُنْدُبِ بْنِ سُفْيَانَ، قَالَ دَمِيَتْ إِصْبَعُ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي بَعْضِ تِلْكَ الْمَشَاهِدِ فَقَالَ " هَلْ أَنْتِ إِلاَّ إِصْبَعٌ دَمِيتِ وَفِي سَبِيلِ اللَّهِ مَا لَقِيتِ " .
also referenced under: Book 32, Hadith 136 (In-Book) & Hadith 1796 (Reference)