Tafsir of Al-Hujurat 49:10

إنما المومنون إخوة

The believers are but a brotherhood. means, all of them are brothers in Islam. The Messenger of Allah said,

المسلم أخو المسلم ﻻ يظلمه وﻻ يسلمه

The Muslim is the brother of the Muslim, he is not unjust with him nor does he forsake him. In the Sahih,

والله في عون العبد ما كان العبد في عون أخيه

Allah helps the servant as long as the servant helps his brother. Also in the Sahih:

إذا دعا المسلم ﻻخيه بظهر الغيب قال الملك آمين ولك بمثله

If the Muslim invokes Allah for the benefit of his absent brother, the angel says afterwards, "Amin, and for you the same.'' There are many Hadiths with this meaning, such as, in the Sahih,

مثل المومنين في توادهم وتراحمهم وتواصلهم كمثل الجسد الواحد إذا اشتكى منه عضو تداعى له ساير الجسد بالحمى والسهر

The parable of the believers in relation to the kindness, mercy and compassion they have for each other, is that of the body: when an organ of it falls ill, the rest of the body responds with fever and sleeplessness. And also in Sahih

المومن للمومن كالبنيان يشد بعضه بعضا

A believer to another believer is like a building whose different parts enforce each other. The Prophet then clasped his hands with the fingers interlaced. Allah's statement,

فٲصلحوا بين أخويكم

So make reconciliation between your brothers, refers to the two groups that fight each other,

واتقوا الله

and have Taqwa of Allah (in all of your affairs),

لعلكم ترحمون

that you may receive mercy. and this is a promise from Allah that He will grant mercy to those who fear and obey Him