Al-Adab Al-Mufrad, Book 13, Hadith 259 (English) ⓘ

Abu Hurayra reported that the Prophet, may Allah bless him and grant him peace, said, "Anyone who attributes words to me which I did not say should take his seat in the Fire. Anyone who gives his Muslim brother misguided advice when they consult him has betrayed them. If anyone gives a fatwa which is not firm, the wrong action of that rests on the one who gave the fatwa."

حَدَّثَنَا عَبْدُ اللهِ بْنُ يَزِيدَ قَالَ‏:‏ حَدَّثَنِي سَعِيدُ بْنُ أَبِي أَيُّوبَ قَالَ‏:‏ حَدَّثَنِي بَكْرُ بْنُ عَمْرٍو، عَنْ أَبِي عُثْمَانَ مُسْلِمِ بْنِ يَسَارٍ، عَنْ أَبِي هُرَيْرَةَ قَالَ‏:‏ قَالَ النَّبِيُّ صلى الله عليه وسلم‏:‏ مَنْ تَقَوَّلَ عَلَيَّ مَا لَمْ أَقُلْ، فَلْيَتَبَوَّأْ مَقْعَدَهُ مِنَ النَّارِ وَمَنِ اسْتَشَارَهُ أَخُوهُ الْمُسْلِمُ، فَأَشَارَ عَلَيْهِ بِغَيْرِ رُشْدٍ فَقَدْ خَانَهُ وَمَنْ أُفْتِيَ فُتْيَا بِغَيْرِ ثَبْتٍ، فَإِثْمُهُ عَلَى مَنْ أَفْتَاهُ‏.‏