Following the Sunna of the Prophet (saws) Sahih al-Bukhari 7278, 7279
Arabic hadith text
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا سُفْيَانُ، حَدَّثَنَا الزُّهْرِيُّ، عَنْ عُبَيْدِ اللَّهِ، عَنْ أَبِي هُرَيْرَةَ، وَزَيْدِ بْنِ خَالِدٍ، قَالاَ كُنَّا عِنْدَ النَّبِيِّ صلى الله عليه وسلم فَقَالَ "لأَقْضِيَنَّ بَيْنَكُمَا بِكِتَابِ اللَّهِ "
Translation
Narrated Abu Huraira and Zaid bin Khalid
We were with the Prophet (ﷺ) when he said (to two men), "I shall judge between you according to Allah's Book (Laws)."