The Prophet ﷺ said, "If any of you is tested with the responsibility of judging between Muslims, let him not pass judgment while he is angry. Let him treat the disputants equally in his glance, in seating, and in gesture, and let him not raise his voice over one party rather than the other."
عن النبي ﷺ أنه قال: إذا ابتلي أحدكم بالقضاء بين المسلمين فلا يقضين وهو غضبان، فليسو بينهم بالنظر والمجلس والإشارة، ولا يرفع صوته على أحد الخصمين.
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Daraqutni (4/205), Bayhaqi (13/135), Abu Yaala (5867), and Tabarani in Al-Kabir (23/284) all narrated it through various chains from Abbad bin Kathir, from Abu Abdullah, from Ata bin Yasar, from Umm Salama, and I have already mentioned it. Some of them narrated it in an abridged form.I say, Bayhaqi said, "This chain of transmission contains weakness," meaning Abbad bin Kathir Thaqafi Basri, who is considered daif by the scholars, though he has a corroborating narration.Ishaq bin Rahawayh (1846) narrated it from Baqiya bin Walid, who said, Abu Muhammad told me, from Abu Bakr the freedman of Banu Tamim, from Ata bin Yasar with his chain, mentioning it in a similar way. Abu Muhammad here is unknown, and when Baqiya bin Walid narrates using a kunya, it is usually a sign of weakness. The two chains strengthen each other.