Umar on Brothers: Assume good from your brother, give excuses

Ibn Abi Mulaykah reported: Umar ibn al-Khattab, may Allah be pleased with him, said, “It is not allowed for a Muslim who hears a word from his brother to assume evil of him if he can find something good about it.”

Source: al-Tamhīd 18/20

عَنِ ابْنِ أَبِي مُلَيْكَةَ أَنَّ عُمَرَ بْنَ الْخَطَّابِ رضي الله عنه قَالَ لَا يَحِلُّ لِامْرِئٍ مُسْلِمٍ سَمِعَ مِنْ أَخِيهِ كَلِمَةً أَنْ يَظُنَّ بِهَا سُوءًا وَهُوَ يَجِدُ لَهَا فِي شَيْءٍ مِنَ الْخَيْرِ مَصْدَرًا

التمهيد  لابن عبد البر 18/20