An-Nu’man ibn Bashir (r.a.) reported that the Messenger of Allah, (s.a.w.s.), said, “The metaphor of the believers in their mutual love, mercy and affection is that of the body. When one limb of it (the body) complains, the rest of the body collapses with sleeplessness and fever.”
[Agreed upon]
“A believer is a mirror to his brother. A believer is a brother of a believer: he protects him against any danger and guards him from behind.”
[Related by Al Bukhari in Al Adab Al Mufrad and by Abu Dawood.]