Mishkat al-Masabih 2138
Al-Hārith al-A‘war said:
While passing in the mosque I found the people engrossed in talk, so I went to visit ‘Alī and told him. He asked if that was really so, and when I assured him that it was, he said he had heard God’s messenger say, “Dissension will certainly come,” and asked him how it could be avoided, to which he replied, “God’s Book is the way, for it contains information of what has happened before you, news of what will happen after you, and a decision regarding matters which occur among you (This is explained as a reference to such matters as unbelief and faith, obedience and dis-obedience, what is lawful and what is forbidden, etc.). It is the distinguisher and is not jesting, (Qur’ān, 86:13). If any overweening person abandons it God will break him, and if anyone seeks guidance elsewhere God will lead him astray. It is God’s strong cord, it is the wise reminder, it is the straight path, it is that by which the desires do not swerve nor the tongues become confused, and the learned cannot grasp it completely.* It does not become worn out by repetition and its wonders do not come to an end. It is that of which the jinn did not hesitate to say when they heard it, ‘We have heard a wonderful recital which guides to what is right, and we believe in it,’ (Qur’ān, 72). He who utters it speaks the truth, he who acts according to it is rewarded, he who pronounces judgment according to it is just, and he who invites people to it guides to a straight path.” 
*The verb used is one ordinarily meaning 'to be satisfied'. Here it is used to indicate that the learned can never learn all there is to be known about the teaching and meaning of the Qur’ān, so that they should be satisfied and feel no need to continue their study of it.  

Tirmidhī and Dārimī transmit­ted it, Tirmidhī saying this is a tradition whose isnād is unknown, and al-Hārith is adversely criticised.
وَعَنِ الْحَارِثِ الْأَعْوَرِ قَالَ: مَرَرْتُ فِي الْمَسْجِدِ فَإِذَا النَّاسُ يَخُوضُونَ فِي الْأَحَادِيثِ فَدَخَلْتُ عَلَى عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ فَأَخْبَرْتُهُ قَالَ: أَوَقَدْ فَعَلُوهَا؟ قلت نعم قَالَ: أما إِنِّي قَدْ سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُول: «أَلا إِنَّهَا سَتَكُون فتْنَة» . فَقلت مَا الْمَخْرَجُ مِنْهَا يَا رَسُولَ اللَّهِ قَالَ: «كتاب الله فِيهِ نبأ مَا كَانَ قبلكُمْ وَخبر مَا بعدكم وَحكم مَا بَيْنكُم وَهُوَ الْفَصْلُ لَيْسَ بِالْهَزْلِ مَنْ تَرَكَهُ مِنْ جَبَّارٍ قَصَمَهُ اللَّهُ وَمَنِ ابْتَغَى الْهُدَى فِي غَيْرِهِ أَضَلَّهُ اللَّهُ وَهُوَ حَبْلُ اللَّهِ الْمَتِينُ وَهُوَ الذِّكْرُ الْحَكِيمُ وَهُوَ الصِّرَاطُ الْمُسْتَقِيمُ هُوَ الَّذِي لَا تَزِيغُ بِهِ الْأَهْوَاءُ وَلَا تَلْتَبِسُ بِهِ الْأَلْسِنَةُ وَلَا يَشْبَعُ مِنْهُ الْعُلَمَاءُ وَلَا يَخْلِقُ على كَثْرَةِ الرَّدِّ وَلَا يَنْقَضِي عَجَائِبُهُ هُوَ الَّذِي لَمْ تَنْتَهِ الْجِنُّ إِذْ سَمِعَتْهُ حَتَّى قَالُوا (إِنَّا سَمِعْنَا قُرْآنًا عَجَبًا يَهْدِي إِلَى الرُّشْدِ فَآمَنا بِهِ)
مَنْ قَالَ بِهِ صَدَقَ وَمَنْ عَمِلَ بِهِ أُجِرَ وَمَنْ حَكَمَ بِهِ عَدَلَ وَمَنْ دَعَا إِلَيْهِ هُدِيَ إِلَى صِرَاطٍ مُسْتَقِيمٍ» . رَوَاهُ التِّرْمِذِيُّ وَالدَّارِمِيُّ وَقَالَ التِّرْمِذِيُّ: هَذَا حَدِيثٌ إِسْنَادُهُ مَجْهُولٌ وَفِي الْحَارِث مقَال