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.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
darimi:161 – ʿAbdullāh b. Yazīd > Saʿīd b. Abū Ayyūb > Bakr b. ʿAmr al-Maʿāfirī > Abū ʿUthmān Muslim b. Yasār > Abū Hurayrah Rḍy Allāh ʿNh

[Machine] From him, from the Prophet ﷺ : "Whoever is given a fatwa (religious ruling) by someone who is not firm (knowledgeable/qualified), then indeed his sin is upon the one who gave him the fatwa."  

الدارمي:١٦١ – أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ يَزِيدَ حَدَّثَنَا سَعِيدُ بْنُ أَبِي أَيُّوبَ حَدَّثَنِي بَكْرُ بْنُ عَمْرٍو الْمَعَافِرِيُّ عَنْ أَبِي عُثْمَانَ مُسْلِمِ بْنُ يَسَارٍ عَنْ أَبِي هُرَيْرَةَ رضي الله

عنه عَنِ النَّبِيِّ ﷺ «مَنْ أُفْتِيَ بِفُتْيَا مَنْ غَيْرِ ثَبْتٍ فَإِنَّمَا إِثْمُهُ عَلَى مِنْ أَفْتَاهُ»  

See similar narrations below:

Collected by Ibn Mājah, Suyūṭī
ibnmajah:53 – Abū Bakr b. Abū Shaybah > ʿAbdullāh b. Yazīd > Saʿīd b. Abū Ayyūb > Abū Hāniʾ Ḥumayd b. Hāniʾ al-Khawlānī > Abū ʿUthmān Muslim b. Yasār > Abū Hurayrah

"The Messenger of Allah ﷺ said: 'Whoever is given a Fatwa (verdict) that has no basis, then his sin will be upon the one who issued that Fatwa.'"  

ابن ماجة:٥٣ – حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يَزِيدَ عَنْ سَعِيدِ بْنِ أَبِي أَيُّوبَ حَدَّثَنِي أَبُو هَانِئٍ حُمَيْدُ بْنُ هَانِئٍ الْخَوْلاَنِيُّ عَنْ أَبِي عُثْمَانَ مُسْلِمِ بْنِ يَسَارٍ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ أُفْتِيَ بِفُتْيَا غَيْرَ ثَبَتٍ فَإِنَّمَا إِثْمُهُ عَلَى مَنْ أَفْتَاهُ