Allah the Exalted said:
رياض الصالحينAbū Zakariyyā Muḥyī al-Dīn Yaḥyā ibn Sharaf al-Nawawī٢٧٣ - باب تحريم احتقار المسلمين
٢٧٣ - باب تحريم احتقار المسلمين
O you who have believed, let not a people ridicule [another] people; perhaps they may be better than them; nor let women ridicule [other] women; perhaps they may be better than them. And do not insult one another and do not call each other by [offensive] nicknames. Wretched is the name [i.e., mention] of disobedience after [one's] faith. And whoever does not repent - then it is those who are the wrongdoers.
And the Exalted said:
وَيْلٌ لِّكُلِّ هُمَزَةٍ لُّمَزَةٍ
Woe to every scorner and mocker
وعن أَبي هريرة - ﵁: أنَّ رسولَ اللهِ - ﷺ - قَالَ: «بِحَسْبِ امْرِئٍ مِنَ الشَّرِّ أَنْ يَحْقِرَ أَخَاهُ المُسْلِمَ». رواه مسلم، وَقَدْ سبق قريبًا بطوله.
Abū Hurayra (may Allah be pleased with him) reported that the Messenger of Allah ﷺ said: "It is enough evil for a man that he should despise his Muslim brother." Narrated by Muslim, and it has already been given in full a short way back.
وعن ابن مسعودٍ - ﵁ - عن النبيّ - ﷺ - قَالَ: «لا يَدْخُلُ الجَنَّةَ مَنْ كَانَ فِي قَلْبِهِ مِثْقَالُ ذَرَّةٍ مِنْ كِبْرٍ!» فَقَالَ رَجُلٌ: إنَّ الرَّجُلَ يُحِبُّ أَنْ يَكُونَ ثَوْبُهُ حَسَنًا، وَنَعْلُهُ حَسَنةً، فَقَالَ: «إنَّ اللهَ جَمِيلٌ يُحِبُّ الجَمَالَ، الكِبْرُ: بَطَرُ الحَقِّ، وَغَمْطُ النَّاسِ». رواه مسلم. ومعنى «بَطَرُ الحَقِّ» دَفْعُه، «وغَمْطُهُمْ»: احْتِقَارُهُمْ، وَقَدْ سَبَقَ بَيَانُهُ أوْضَحَ مِنْ هَذَا في باب الكِبْرِ.
Ibn Masʿūd (may Allah be pleased with him) reported from the Prophet ﷺ that he said: "No one will enter Paradise who has in his heart the weight of an atom of arrogance." A man said: A man likes his garment to be fine and his sandals to be fine. He said: "Indeed Allah is beautiful and loves beauty. Arrogance is rejecting the truth and despising people." Narrated by Muslim. The meaning of "rejecting the truth" is repelling it, and "despising them" is holding them in contempt; its explanation has already come, clearer than this, in the chapter on arrogance.
وعن جُندب بن عبدِ الله - ﵁ - قَالَ: قَالَ رسولُ اللهِ - ﷺ: «قَالَ رَجُلٌ: وَاللهِ لاَ يَغْفِرُ اللهُ لِفُلانٍ، فَقَالَ اللهُ - ﷿: مَنْ ذا الَّذِي يَتَأَلَّى عَلَيَّ أَنْ لا أغْفِرَ لِفُلانٍ! فَإنِّي قَدْ غَفَرْتُ لَهُ، وَاحْبَطْتُ عَمَلَكَ». رواه مسلم.
Jundub ibn ʿAbd Allāh (may Allah be pleased with him) said: The Messenger of Allah ﷺ said: "A man said: By Allah, Allah will not forgive so-and-so. So Allah, Mighty and Majestic, said: Who is this who swears by Me that I will not forgive so-and-so? I have indeed forgiven him and nullified your deeds." Narrated by Muslim.