Narrated 'Ali (RA):

Allah's Messenger (ﷺ) said: "When two men bring a case before you, do not decide in favor of the first till you hear what the other has to say, then you will know how to judge." 'Ali (RA) said: "Since then, I have continued to judge (in accordance with that)." [Reported by Ahmad, Abu Dawud and at-Tirmidhi. The latter graded it Hasan (good), while Ibn al-Madini graded it Qawi (strong), and Ibn Hibban graded it Sahih (authentic).]

وَعَنْ عَلِيٍّ ‏- رضى الله عنه ‏- قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{

إِذَا تَقَاضَى إِلَيْكَ رَجُلَانِ, فَلَا تَقْضِ لِلْأَوَّلِ, حَتَّى تَسْمَعَ كَلَامَ اَلْآخَرِ, فَسَوْفَ تَدْرِي كَيْفَ تَقْضِي

.‏ قَالَ [1]‏ .‏ عَلِيٌّ: فَمَا زِلْتُ قَاضِيًا بَعْدُ } رَوَاهُ أَحْمَدُ, وَأَبُو دَاوُدَ, وَاَلتِّرْمِذِيُّ وَحَسَّنَهُ, وَقَوَّاهُ اِبْنُ اَلْمَدِينِيُّ, وَصَحَّحَهُ اِبْنُ حِبَّانَ [2]‏ .‏