Surah Yunus — Ayah 36 (10:36)
وَمَا يَتَّبِعُ أَكۡثَرُهُمۡ إِلَّا ظَنًّاۚ إِنَّ ٱلظَّنَّ لَا يُغۡنِي مِنَ ٱلۡحَقِّ شَيۡـًٔاۚ إِنَّ ٱللَّهَ عَلِيمُۢ بِمَا يَفۡعَلُونَ ٣٦
English translation (Saheeh International)
And most of them follow not except assumption. Indeed, assumption avails not against the truth at all. Indeed, Allāh is Knowing of what they do.
Brief commentary
Most of the idolaters only follow matters that they have no knowledge about, only guessing and assuming. Mere assumption cannot take the place of knowledge and can be of no use against it. Allah knows all that they do, nothing of what they do is hidden from Him, and they will be rewarded accordingly.