When a judge gives a decision, having tried his best to decide correctly and is right, there are two rewards for him; and if he gave a judgment after having tried his best (to arrive at a correct decision) but erred, there is one reward for him.  

أَنَّهُ سَمِعَ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ ثُمَّ أَصَابَ فَلَهُ أَجْرَانِ وَإِذَا حَكَمَ فَاجْتَهَدَ ثُمَّ أَخْطَأَ فَلَهُ أَجْرٌ  

"The Messenger of Allah [SAW] said: 'If a judge passes judgment and strives to reach the right conclusion and gets it right, he will have two rewards; if he strives to reach the right conclusion but gets it wrong, he will still have one reward."  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ فَأَصَابَ فَلَهُ أَجْرَانِ وَإِذَا اجْتَهَدَ فَأَخْطَأَ فَلَهُ أَجْرٌ  

'If a judge passes a judgment having exerted himself to arrive at what is correct, and he is indeed correct, he will have two rewards. If he passes judgment having exerted himself to arrive at what is correct, but it is incorrect, he will have one reward.'" I narrated it to Abu Bakr bin Hazm and he said: "This is what Abu Salamah narrated to me from Abu Hurairah.  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ فَأَصَابَ فَلَهُ أَجْرَانِ وَإِذَا حَكَمَ فَاجْتَهَدَ فَأَخْطَأَ فَلَهُ أَجْرٌ فَحَدَّثْتُ بِهِ أَبَا بَكْرِ بْنَ حَزْمٍ فَقَالَ هَكَذَا حَدَّثَنِي أَبُو سَلَمَةَ عَنْ أَبِي هُرَيْرَةَ  

"When the judge passes a judgement in which he strived and was correct, then he receives two rewards. And when he judges and is mistaken, then he receives one reward."  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ فَأَصَابَ فَلَهُ أَجْرَانِ وَإِذَا حَكَمَ فَأَخْطَأَ فَلَهُ أَجْرٌ وَاحِدٌ قَالَ وَفِي الْبَابِ عَنْ عَمْرِو بْنِ الْعَاصِي وَعُقْبَةَ بْنِ عَامِرٍ  

“When the judge passes a judgement and does his best and gets it right, he will have two rewards, and if he passes a judgement and does his best and gets it wrong, he will have one reward.” (Sahih) Yazid (one of narrators) said : “So I Narrated it to Abu Bakr bin 'Amr bin Hazm. He said: 'This is how it was narrated to me by Abu Salamah from Abu Hurairah.'”  

أَنَّهُ سَمِعَ رَسُولَ اللَّهِ ﷺ يَقُولُ إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ فَأَصَابَ فَلَهُ أَجْرَانِ وَإِذَا حَكَمَ فَاجْتَهَدَ فَأَخْطَأَ فَلَهُ أَجْرٌ قَالَ يَزِيدُ فَحَدَّثْتُ بِهِ أَبَا بَكْرِ بْنَ عَمْرِو بْنِ حَزْمٍ فَقَالَ هَكَذَا حَدَّثَنِيهِ أَبُو سَلَمَةَ عَنْ أَبِي هُرَيْرَةَ  

That he heard Messenger of Allah ﷺ saying, "If a judge gives a verdict according to the best of his knowledge and his verdict is correct (i.e. agrees with Allah and His Apostle's verdict) he will receive a double reward, and if he gives a verdict according to the best of his knowledge and his verdict is wrong, (i.e. against that of Allah and His Apostle) even then he will get a reward ." (Using translation from Bukhārī 7352)  

أَنَّهُ سَمِعَ رَسُولَ اللهِ ﷺ يَقُولُ إِذَا حَكَمَ الْحَاكِمُ وَاجْتَهَدَ ثُمَّ أَصَابَ فَلَهُ أَجْرَانِ وَإِذَا حَكَمَ وَاجْتَهَدَ ثُمَّ أَخْطَأَ فَلَهُ أَجْرٌ  

"The Messenger of Allah [SAW] said: 'If a judge passes judgment and strives to reach the right conclusion and gets it right, he will have two rewards; if he strives to reach the right conclusion but gets it wrong, he will still have one reward." (Using translation from Nasāʾī 5381)  

قَالَ رَسُولُ اللَّهِ ﷺ «إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ فَأَصَابَ فَلَهُ أَجْرَانِ وَإِذَا حَكَمَ فَاجْتَهَدَ فَأَخْطَأَ فَلَهُ أَجْرٌ»  

"The Messenger of Allah [SAW] said: 'If a judge passes judgment and strives to reach the right conclusion and gets it right, he will have two rewards; if he strives to reach the right conclusion but gets it wrong, he will still have one reward." (Using translation from Nasāʾī 5381)  

قَالَ رَسُولُ اللهِ ﷺ «إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ فَأَصَابَ فَلَهُ أَجْرَانِ وَإِذَا اجْتَهَدَ فَأَخْطَأَ فَلَهُ أَجْرٌ»  

[Machine] About the Prophet ﷺ , he said: "When a judge makes a decision and strives hard, and he is correct, he will have two rewards. And if he makes a decision and strives hard, but he is mistaken, he will still have a reward. This is reported only by Ma'mar, who narrated it from Sufyan and no one else."  

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا حَكَمَ الْحَاكِمُ فَاجْتَهَدَ فَأَصَابَ فَلَهُ أَجْرَانِ وَإِذَا حَكَمَ فَاجْتَهَدَ فَأَخْطَأَ فَلَهُ أَجْرٌ لَمْ يَرْوِهِ عَنْ سُفْيَانَ إِلَّا مَعْمَرٌ تَفَرَّدَ بِهِ عَنْهُ عَبْدُ الرَّزَّاقِ  

When a judge gives a decision, having tried his best to decide correctly and is right, there are two rewards for him; and if he gave a judgment after having tried his best (to arrive at a correct decision) but erred, there is one reward for him. (Using translation from Muslim 1716a)   

"إذا حَكَمَ الحَاكِم فَاجْتَهدَ؛ فَأصَابَ؛ فَلَهُ أَجْرَانِ، وَإِذَا حَكَمَ فَاجْتَهَدَ؛ فَاخْطَأَ فَلَه أجْرٌ وَاحِدٌ".