Surah Al Hujurat Verse 12 explains the prohibition against prejudice, finding fault with others and using it because it is tantamount to eating the flesh of a dead brother.
Surah Al Hujurat Verse 12 in Arabic, Transliteration, and English Translation
يٰٓاَيُّهَا الَّذِيْنَ اٰمَنُوا اجْتَنِبُوْا كَثِيْرًا مِّنَ الظَّنِّۖ اِنَّ بَعْضَ الظَّنِّ اِثْمٌ وَّلَا تَجَسَّسُوْا وَلَا يَغْتَبْ بَّعْضُكُمْ بَعْضًاۗ اَيُحِبُّ اَحَدُكُمْ اَنْ يَّأْكُلَ لَحْمَ اَخِيْهِ مَيْتًا فَكَرِهْتُمُوْهُۗ وَاتَّقُوا اللّٰهَ ۗاِنَّ اللّٰهَ تَوَّابٌ رَّحِيْمٌ
Yā ayyuhallażīna āmanujtanibụ kaṡīram minaẓ-ẓanni inna ba’ḍaẓ-ẓanni iṡmuw wa lā tajassasụ wa lā yagtab ba’ḍukum ba’ḍā, a yuḥibbu aḥadukum ay ya`kula laḥma akhīhi maitan fa karihtumụh, wattaqullāh, innallāha tawwābur raḥīm
“O people of faith! Stay away from many prejudices, indeed some prejudices are sins and do not find fault with others and do not let any of you use some of the others. Do any of you like to eat the flesh of his dead brother? Of course you feel disgusted. And be devoted to Allah, verily Allah is all-beneficiary, all-merciful.” (Q.S Al Hujurat : 12)
O people of faith! Stay away from many of the prejudices against people that are not accompanied by evidence or signs, indeed some prejudices, that is, prejudices that are not accompanied by evidence or signs that are sinful and do not find fault with others who deliberately cover up to ridicule them and let none of you use it, that is, talk about disgrace, some others.
Do any of you like to eat the flesh of his dead brother? Of course, you feel disgusted. Therefore avoid slavery because it is the same as eating the flesh of a dead brother. And be devoted to Allah, verily Allah is all-repentant to the repentant, all-merciful to the obedient.