Hadith 31-287

وَبِإِسْنادِهِ عَنْ عَلِيِ‏ عَلَيْهِ السَّلامُ قالَ: إِنَّ النَّبِيُ‏ صَلَّى اللهُ عَلَيْهِ وَآلِهِ لَمّا وَجَّهَني إِلى الَيمَنِ قالَ: إِذا تُحُوكُم إِلَيكَ فَلا تَحكُم لاحَدِ الخَصمَينِ دوُنَ أَن تَسمَعَ مِنَ الآخَرِ، قالَ: فَما شَكَكْتُ فِي قِضاءِ بَعْدَ ذلِكَ.

According to the same documentation, it is narrated that Ali (a.s.) said, “When the Prophet (S) sent me to take over the post of the governor of Yemen, he (a.s.) said, ‘Whenever you are faced with a case to judge, do not make a ruling before you hear what the other side has to say in his own defense.’ From then on I never had any doubts about my judgements.”