The Qur'anic verse: "If they do come to thee, either judge between them, or decline to interfere" was abrogated by the verse: "So judge between them by what Allah hath revealed."  

{ فَإِنْ جَاءُوكَ فَاحْكُمْ بَيْنَهُمْ أَوْ أَعْرِضْ عَنْهُمْ } فَنُسِخَتْ قَالَ { فَاحْكُمْ بَيْنَهُمْ بِمَا أَنْزَلَ اللَّهُ }  

When this verse was revealed: "If they do come to thee, either judge between them, or decline to interfere....If thou judge, judge in equity between them." Banu an-Nadir used to pay half blood-money if they killed any-one from Banu Qurayzah. When Banu Qurayzah killed anyone from Banu an-Nadir, they would pay full blood-money. So the Messenger of Allah ﷺ made it equal between them.  

لَمَّا نَزَلَتْ هَذِهِ الآيَةُ { فَإِنْ جَاءُوكَ فَاحْكُمْ بَيْنَهُمْ أَوْ أَعْرِضْ عَنْهُمْ } { وَإِنْ حَكَمْتَ فَاحْكُمْ بَيْنَهُمْ بِالْقِسْطِ } الآيَةَ قَالَ كَانَ بَنُو النَّضِيرِ إِذَا قَتَلُوا مِنْ بَنِي قُرَيْظَةَ أَدَّوْا نِصْفَ الدِّيَةِ وَإِذَا قَتَلَ بَنُو قُرَيْظَةَ مِنْ بَنِي النَّضِيرِ أَدَّوْا إِلَيْهِمُ الدِّيَةَ كَامِلَةً فَسَوَّى رَسُولُ اللَّهِ ﷺ بَيْنَهُمْ