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
quran:10:36 –

And most of them follow not except assumption. Indeed, assumption avails not against the truth at all. Indeed, Allah is Knowing of what they do.  

And most of them, in worshipping idols, follow nothing but conjecture, since they imitate their fathers therein; truly conjecture avails nothing against truth, when what is sought is knowledge. Surely God is Knower of what they do, and will requite them for it.
القرآن:١٠:٣٦ –

وَمَا يَتَّبِعُ أَكْثَرُهُمْ إِلَّا ظَنًّا ۚ إِنَّ الظَّنَّ لَا يُغْنِي مِنَ الْحَقِّ شَيْئًا ۚ إِنَّ اللَّهَ عَلِيمٌ بِمَا يَفْعَلُونَ  

{وما يتبع أكثرهم} في عبادة الأصنام {إلا ظنا} حيث قلدوا فيه آباءهم {إن الظن لا يُغني من الحق شيئا} فيما المطلوب منه العلم {إن الله عليم بما يفعلون} فيجازيهم عليه.

See similar narrations below:

Collected by Qurʾān
quran:53:28 –

And they have thereof no knowledge. They follow not except assumption, and indeed, assumption avails not against the truth at all.  

But they do not have any knowledge thereof, of this claim. They follow, in this ˹respect˺, nothing but conjecture, which they have conjured up, and indeed conjecture can never substitute for the truth, that is to say, when it comes to acquiring knowledge of that which one is required to have knowledge of.
القرآن:٥٣:٢٨ –

وَمَا لَهُمْ بِهِ مِنْ عِلْمٍ ۖ إِنْ يَتَّبِعُونَ إِلَّا الظَّنَّ ۖ وَإِنَّ الظَّنَّ لَا يُغْنِي مِنَ الْحَقِّ شَيْئًا  

{وما لهم به} بهذا القول {من علم إن} ما {يتبعون} فيه {إلا الظن} الذي تخيلوه {وإن الظن لا يغني من الحق شيئا} أي عن العلم فيما المطلوب فيه العلم.