Sahih Muslim 1768bBook 32, Hadith 78
وَحَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، عَنْ شُعْبَةَ، بِهَذَا الإِسْنَادِ وَقَالَ فِي حَدِيثِهِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لَقَدْ حَكَمْتَ فِيهِمْ بِحُكْمِ اللَّهِ " . وَقَالَ مَرَّةً " لَقَدْ حَكَمْتَ بِحُكْمِ الْمَلِكِ " .
You have adjudged according to the command of God. And once he said: you have adjudged by the decision of a king.