Dāwud bin Amr aḍ-Ḍabbī narrated to us, Nāfi’ bin Umar narrated to us, on authority of Ibn Abī Mulaykah, he said: ‘I wrote to Ibn Abbās asking him to write something for me and he withheld from me quite a bit, and said: ‘As a sincere child, I will write for him something especially suited to his status withholding from him what would not benefit him’. said: ‘So called for the judgment of Alī , and he began to write from it and he came upon something . So said: ‘By Allah, Alī did not give judgment according to this unless he was astray’.’
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا دَاوُدُ بْنُ عَمْرٍو الضَّبِّيُّ، حَدَّثَنَا نَافِعُ بْنُ عُمَرَ، عَنِ ابْنِ أَبِي مُلَيْكَةَ، قَالَ كَتَبْتُ إِلَى ابْنِ عَبَّاسٍ أَسْأَلُهُ أَنْ يَكْتُبَ، لِي كِتَابًا وَيُخْفِي عَنِّي . فَقَالَ وَلَدٌ نَاصِحٌ أَنَا أَخْتَارُ لَهُ الأُمُورَ اخْتِيَارًا وَأُخْفِي عَنْهُ . قَالَ فَدَعَا بِقَضَاءِ عَلِيٍّ فَجَعَلَ يَكْتُبُ مِنْهُ أَشْيَاءَ وَيَمُرُّ بِهِ الشَّىْءُ فَيَقُولُ وَاللَّهِ مَا قَضَى بِهَذَا عَلِيٌّ إِلاَّ أَنْ يَكُونَ ضَلَّ .
sunnah.com