In Hojorat sura, verse no. 10 Allah Almighty said:

إِنَّمَا الْمُؤْمِنُونَ إِخْوَةٌ فَأَصْلِحُوا بَيْنَ أَخَوَيْكُمْ ۚ وَاتَّقُوا اللَّهَ لَعَلَّكُمْ تُرْحَمُونَ

The faithful are indeed brothers. Therefore, make peace between your brothers and be wary of Allah, so that you may receive [His] mercy.

Important points:

This verse considers the relationship of believers with each other as the relationship of two brothers, which contains some points in this interpretation, such as:

A) The friendship between two brothers is deep and stable.

b) The friendship between two brothers is mutual, not one sided.

c) The friendship of two brothers is based on nature and not on material and worldly attractions.

d) Two brothers are united against a stranger and they are each other's arms.

e) The origin of two brothers is one.

f) Paying attention to brotherhood is a matter of passing and turning a blind eye.

g) He is happy when he is happy and sad when he is sad.

Today, the words friend, friend, fellow citizen and fellow countryman are used to express interest, but Islam used the word brother, which is the deepest word.