Musnad Ahmad 1145
It was narrated that `Amr bin Murrah said:
I heard Abul-Bakhtari At-Ta`i say: Someone who heard ‘Ali (رضي الله عنها) told me that he said: When the Messenger of Allah (ﷺ) sent me to Yemen, I said: Are you sending me when I am young and I do not know much about judging? The Messenger of Allah (ﷺ) struck my chest and said: Go, for Allah, may He be glorified and exalted, will make your tongue steadfast and guide your heart.` He said: I never found it difficult to judge between two people.
حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ عَمْرِو بْنِ مُرَّةَ، قَالَ سَمِعْتُ أَبَا الْبَخْتَرِيِّ الطَّائِيَّ، قَالَ أَخْبَرَنِي مَنْ، سَمِعَ عَلِيًّا، رَضِيَ اللَّهُ عَنْهُ يَقُولُ لَمَّا بَعَثَنِي رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِلَى الْيَمَنِ فَقُلْتُ تَبْعَثُنِي وَأَنَا رَجُلٌ حَدِيثُ السِّنِّ وَلَيْسَ لِي عِلْمٌ بِكَثِيرٍ مِنْ الْقَضَاءِ قَالَ فَضَرَبَ صَدْرِي رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَقَالَ اذْهَبْ فَإِنَّ اللَّهَ عَزَّ وَجَلَّ سَيُثَبِّتُ لِسَانَكَ وَيَهْدِي قَلْبَكَ قَالَ فَمَا أَعْيَانِي قَضَاءٌ بَيْنَ اثْنَيْنِ‏.‏