Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
ahmad-zuhd:635 – ʿAbdullāh > Bī > Hushaym > Manṣūr > al-Ḥasan > Qawm Qadimūā > ʿĀmil Liʿumar b. al-Khaṭṭāb ؒ Faʾajāz al-ʿArab And Tarak al-Mawālī Fabalagh Dhalik ʿUmar > Fakatab Ilayh Biḥasb al-Muʾmin from al-Shar

[Machine] "That a Muslim should not belittle his fellow Muslim."  

الزهد لأحمد:٦٣٥ – حَدَّثَنَا عَبْدُ اللَّهِ حَدَّثَنِي أبِي حَدَّثَنَا هُشَيْمٌ أَنْبَأَنَا مَنْصُورٌ عَنِ الْحَسَنِ أَنَّ قَوْمًا قَدِمُوا عَلَى عَامِلٍ لِعُمَرَ بْنِ الْخَطَّابِ رَحِمَهُ اللَّهُ فَأَجَازَ الْعَرَبَ وَتَرَكَ الْمَوَالِيَ فَبَلَغَ ذَلِكَ عُمَرَ قَالَ فَكَتَبَ إِلَيْهِ «بِحَسْبِ الْمُؤْمِنِ مِنَ الشَّرِّ

أَنَّ يَحْقِرَ أَخَاهُ الْمُسْلِمَ»  

See similar narrations below:

Collected by Suyūṭī