The Messenger of Allah ﷺ said, "I am only a human being, and disputes are brought before me. Perhaps one of you is more eloquent in presenting his argument than the other, so I assume he is telling the truth and rule in his favor. Whoever I rule in his favor by taking the right of a Muslim, it is only a piece of Hellfire. Let him take it or leave it."
عن رسول الله ﷺ قال: إنما أنا بشر، وإنه يأتيني الخصم، فلعل بعضكم أن يكون أبلغ من بعض، فأحسب أنه صدق، فأقضي له بذلك، فمن قضيت له بحق مسلم فإنما هي قطعة من النار، فليأخذها أو فليتركها.
Bukhari narrated it in the Book of Wrongs (2458), and Muslim in the Book of Judgments (1713), both from the hadith of Zuhri, who said, Urwa bin Zubayr informed me, that Zaynab bint Umm Salama informed him, that her mother Umm Salama, the wife of the Prophet ﷺ, informed her, and he mentioned it.