Tafsir of Yunus 10:36

وما يتبع أكثرهم إﻻ ظنا إن الظن ﻻ يغني من الحق شييا

And most of them follow nothing but conjecture. Certainly, conjecture can be of no avail against the truth. Allah explained that they did not follow their own religion out of evidence and proof. The fact is that they were following mere conjecture and imagination. But conjecture is in no way a substitute for the truth. He said,

إن الله عليم بما يفعلون

Allah is All-Aware of what they do. This is both a threat and a promise of severe punishment. Allah said that He would reward them for their actions with a complete reward