Kitāb al-Muʾmin

Hadith 85
brotherhood
85 - وعن أحدهما (ع) أنه قال المؤمِن أخو المؤمن كالجسَدِ الواحد، إذا سقط منه شئٌ تَداعى سائرُ الجسد.
85. It has been reported that Abu Ja'far or Abu 'Abd Allah (a.s) said: Believers are brothers of one another, like one physical body from which when one part is lost, the whole body becomes affected.
Source: Ḥusayn b. Saʿīd al-Ahwāzī