Nu'man b. Bashir, reported that Allah's Messenger (ﷺ) had said:

Have you, besides him, other sons? He said: Yes. Thereupon he (the Prophet) said: Have you given gifts to all of them like this (as you have given to Nu'man)? He said: No. Thereupon he (the Prophet) said: I cannot bear witness to an injustice.

حَدَّثَنَا ابْنُ نُمَيْرٍ، حَدَّثَنِي أَبِي، حَدَّثَنَا إِسْمَاعِيلُ، عَنِ الشَّعْبِيِّ، عَنِ النُّعْمَانِ بْنِ بَشِيرٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ أَلَكَ بَنُونَ سِوَاهُ ‏"‏ ‏.‏ قَالَ نَعَمْ ‏.‏ قَالَ ‏"‏ فَكُلَّهُمْ أَعْطَيْتَ مِثْلَ هَذَا ‏"‏ ‏.‏ قَالَ لاَ ‏.‏ قَالَ ‏"‏ فَلاَ أَشْهَدُ عَلَى جَوْرٍ ‏"‏ ‏.‏