Sahih (Sahih Muslim)
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 " .
Through the same chain of transmitters Shu'ba has narrated the same tradition in which he says that the Messenger of Allah (ﷺ) said (to Sa'd):You have adjudged according to the command of God. And once he said: you have adjudged by the decision of a king