236 – Anas (may Allah be pleased with him) relates that the Prophet (peace and blessings be upon him) said, “None of you truly believes until he loves for his brother what he loves for himself.” Agreed upon.

237 – He also reported that the Messenger of Allah (peace and blessings be upon him) said, “Support your brother, whether he is wronging others or is himself wronged.” A man asked, “Messenger of Allah, if he is wronged I can support him, but how do I support him when he is the wrongdoer?” He replied, “By restraining him from wrongdoing—that is your support for him.” Reported by al-Bukhari.

[Explanation]
The author—may Allah have mercy on him—cites the narration of Anas ibn Mālik (may Allah be pleased with him) in which the Prophet (peace and blessings be upon him) said, “None of you truly believes until he loves for his brother what he loves for himself.” “He does not believe” here means: he is not a genuine believer with complete faith unless he meets this condition—that he loves for his brother the same good he loves for himself, and that he desires for his brother to be spared the evil from which he wishes to protect himself; that is, he must dislike for his brother what he dislikes for his own soul. This is the mark of the true believer. A person who treats his fellow Muslims in this way could never cheat them, betray them, lie to them, or assault them, for he would not wish such treatment for himself.

This hadith therefore shows that anyone who dislikes for his brother what he likes for himself, or likes for his brother what he himself dislikes, is not a believer—in other words, his faith is incomplete.

It further indicates that loving for your brother what you detest for yourself is counted among the major sins