Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
darimi:166ʿIṣmah b. al-Faḍl > Zayd b. al-Ḥubāb > Yazīd b. ʿUqbah > al-Ḍaḥḥāk > Jābir b. Zayd

[Machine] He (said to him), "O Abu al-Sha'tha', indeed you are one of the knowledgeable people of Basra, so do not issue fatwas except with a clear Quranic verse or a established Sunnah, for if you do anything different from that, you will be ruined, and you will cause ruin."  

الدارمي:١٦٦أَخْبَرَنَا عِصْمَةُ بْنُ الْفَضْلِ حَدَّثَنَا زَيْدُ بْنُ الْحُبَابِ عَنْ يَزِيدَ بْنِ عُقْبَةَ حَدَّثَنَا الضَّحَّاكُ عَنْ جَابِرِ بْنِ زَيْدٍ أَنَّ ابْنَ عُمَرَ لَقِيَهُ فِي الطَّوَافِ فَقَالَ

لَهُ «يَا أَبَا الشَّعْثَاءِ إِنَّكَ مِنْ فُقَهَاءِ الْبَصْرَةِ فَلَا تُفْتِ إِلَّا بِقُرْآنٍ نَاطِقٍ أَوْ سُنَّةٍ مَاضِيَةٍ فَإِنَّكَ إِنْ فَعَلْتَ غَيْرَ ذَلِكَ هَلَكْتَ وَأَهْلَكْتَ»