Al-Lu'lu Wal-Marjan 1671 — The Book of Kindness, Good Relations and Good Manners

An-Nu'man bin Bashir Narrated from:

Allâh’s Messenger ﷺ said, “You see the believers as regard their being merciful among themselves, showing love among themselves and being kind among themselves, resembling one body, so that, if any part of the body is not well, then the whole body shares the sleeplessness (insomnia) and fever with it.” ( Sahîh Al-Bukhârî, Hadîth No. 40, Vol. 8 )