Mukhtasar Muslim

Sayyiduna Nu’man bin Bashir (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: The example of the believers in their mutual love, mercy, and compassion is like that of a single body; when any limb of it suffers, the whole body responds with sleeplessness and fever. (In the same way, when a calamity befalls a believer, especially one caused by the disbelievers, all believers should feel restless and strive to remedy it.)