(17) باب تَرَاحُمِ الْمُؤْمِنِينَ وَتَعَاطُفِهِمْ وَتَعَاضُدِهِمْ
Nu'man b. Bashir reported that Muslims are like one body of a person; if the eye is sore, the whole body aches, and if the head aches, the whole body aches.
Reference: Sahih Muslim 2586 d
In-book reference: Book 45, Hadith 87
USC-MSA web (English) reference(deprecated numbering scheme): Book 32, Hadith 6261