الْمُؤْمِنُ أَخُو الْمُؤْمِنِ كَالْجَسَدِ الْوَاحِدِ، إِنِ اشْتَكى شَيْئاً مِنْهُ وَجَدَ أَلَمَ ذلِكَ فِي سَائِرِ جَسَدِهِ، وَ أَرْوَاحُهُمَا مِنْ رُوحٍ وَاحِدَةٍ، وَ إِنَّ رُوحَ الْمُؤْمِنِ لَأَشَدُّ اتِّصَالًا بِرُوحِ اللَّهِ مِنِ اتِّصَالِ شُعَاعِ الشَّمْسِ بِهَا.
Imam Ja‘far al-Ṣadiq (as):
A believer is the brother of another believer, like a single body. If a single limb ails then the rest of the body suffers as well; and their souls are also made of one soul. Verily a believer's soul is more connected to the soul of Allah than the rays are to the sun.
Source:
al-Kāfī
Vol3
P425
ID: 16856