Musnad Ahmad 636
It was narrated that ‘Ali (رضي الله عنه) said:
The Messenger of Allah (ﷺ) sent me to Yemen when I was young, I said: You are sending me to people among whom things happen and I do not know how to judge. He said: `Allah will guide your tongue and make your heart steadfast.` And I never doubted any judgement I passed between two people after that.
حَدَّثَنِي يَحْيَى، عَنِ الْأَعْمَشِ، عَنْ عَمْرِو بْنِ مُرَّةَ، عَنْ أَبِي الْبَخْتَرِيِّ، عَنْ عَلِيٍّ، رَضِيَ اللَّهُ عَنْهُ قَالَ بَعَثَنِي رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِلَى الْيَمَنِ وَأَنَا حَدِيثُ السِّنِّ قَالَ قُلْتُ تَبْعَثُنِي إِلَى قَوْمٍ يَكُونُ بَيْنَهُمْ أَحْدَاثٌ وَلَا عِلْمَ لِي بِالْقَضَاءِ قَالَ إِنَّ اللَّهَ سَيَهْدِي لِسَانَكَ وَيُثَبِّتُ قَلْبَكَ قَالَ فَمَا شَكَكْتُ فِي قَضَاءٍ بَيْنَ اثْنَيْنِ بَعْدُ‏.‏