The strongest level of brotherhood is the sense of community, friendship, and common purpose in Islam for the sake of Allah. At this level, the believers work together towards fulfilling the goals of the religion and living out its divine values.

Allah said:

إِنَّمَا الْمُؤْمِنُونَ إِخْوَةٌ فَأَصْلِحُوا بَيْنَ أَخَوَيْكُمْ وَاتَّقُوا اللَّهَ لَعَلَّكُمْ تُرْحَمُونَ

The believers are but brothers, so make reconciliation between your brothers and fear Allah that you may receive mercy.

Surat al-Hujurat 49:10

And Allah said:

وَاعْتَصِمُوا بِحَبْلِ اللَّهِ جَمِيعًا وَلَا تَفَرَّقُوا وَاذْكُرُوا نِعْمَتَ اللَّهِ عَلَيْكُمْ إِذْ كُنتُمْ أَعْدَاءً فَأَلَّفَ بَيْنَ قُلُوبِكُمْ فَأَصْبَحْتُم بِنِعْمَتِهِ إِخْوَانًا

Hold firmly to the rope of Allah all together and do not become divided. Remember the favor of Allah upon you, when you were enemies and he brought your hearts together and you became brothers by his favor.

Surat Ali Imran 3:103

Although we use the word “brotherhood,” what we really mean is a faith-based community that includes both men and women as brothers and sisters in religion.

Allah said:

وَالْمُؤْمِنُونَ وَالْمُؤْمِنَاتُ بَعْضُهُمْ أَوْلِيَاءُ بَعْضٍ ۚ يَأْمُرُونَ بِالْمَعْرُوفِ وَيَنْهَوْنَ عَنِ الْمُنكَرِ وَيُقِيمُونَ الصَّلَاةَ وَيُؤْتُونَ الزَّكَاةَ وَيُطِيعُونَ اللَّهَ وَرَسُولَهُ ۚ أُولَٰئِكَ سَيَرْحَمُهُمُ اللَّهُ ۗ إِنَّ اللَّهَ عَزِيزٌ حَكِيمٌ

The believing men and believing women are allies of one another. They enjoin what is right and forbid what is wrong and establish prayer and give charity and obey Allah and His Messenger. Allah will have mercy upon them, for Allah is Almighty and Wise.

Surat al-Tawba 9:71