Hadith: No man accuses another man of defiant disobedience or accuses him of disbelief except that it rebounds on him if his companion is not like that

عَنْ أَبِي ذَرٍّ رَضِيَ اللَّهُ عَنْهُ أَنَّهُ سَمِعَ النَّبِيَّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يَقُولُ:
«لاَ يَرْمِي رَجُلٌ رَجُلًا بِالفُسُوقِ، وَلاَ يَرْمِيهِ بِالكُفْرِ، إِلَّا ارْتَدَّتْ عَلَيْهِ، إِنْ لَمْ يَكُنْ صَاحِبُهُ كَذَلِكَ».
[صحيح] - [متفق عليه] - [صحيح البخاري: 6045]

Abu Dharr (may Allah be pleased with him) reported that he heard the Prophet (may Allah's peace and blessings be upon him) say:
"No man accuses another man of defiant disobedience or accuses him of disbelief except that it rebounds on him if his companion is not like that."
[Authentic hadith] - [Narrated by Bukhari & Muslim] - [Sahih Bukhari - 6045]

Explanation

The Prophet (may Allah's peace and blessings be upon him) warned that whoever says to another person: You are a defiant sinner, or: You are a disbeliever, if this person is not as he said, then he will be worthy of this mentioned description, and his accusation will rebound on him. However, if this person is as he said, then nothing will rebound on him given that he said the truth.

Benefits from the Hadith

1. It is prohibited to accuse people of disbelief or defiant disobedience without a Shariah-approved justification.
2. Verification is obligatory before making judgments about people.
3. Ibn Daqīq al-‘Īd said: This is a grave threat to whoever falsely accuses a Muslim of being a disbeliever, which is a great dilemma.
4. Ibn Hajar al-‘Asqalāni said: The fact that he does not consequently become a defiant sinner or a disbeliever does not entail that he is not deemed sinful when he said to him: You are a defiant sinner; rather, this situation needs to be tackled in detail. If he meant to advise him or others by clarifying his condition, then this is permissible. However, if he meant to insult, expose, and abuse him, then this is impermissible because he is commanded to conceal his faults and teach him and advise him in a friendly manner. So, whenever he can fulfill this in a lenient manner, then he is not allowed to do it violently because he could be a cause for tempting him and making him insist on such an act, given the fact that many people are too disdainful to accept the command, especially when the one who gives the command is inferior to the one commanded.