This makes clear the proof in Allah Most High’s words:
“They are watered with the same water, yet We make some of them better than others in fruit. Indeed, in that are signs for people who reason.” (al-Ra'd: 4)
Here He demonstrates that He favors some created things over others, despite their sharing the same causes in certain respects. As He says in another verse:
“Do you not see that Allah sends down water from the sky, with which We bring forth fruits of varying colors? And in the mountains are white and red streaks of varying colors, and others intensely black. * Likewise, people, moving creatures, and livestock vary in color. Only those of His servants who have knowledge fear Allah.” (Fātir: 27-28)
If someone says, “They differ in quality and character only because their recipients differ, along with other causes such as air, soil, seeds, and fruit stones,” he is told:
Those recipients and causes are also His work, not anyone else’s. He is the One who prepares the recipients, and He supplies each thing according to what He has prepared it to receive. It thus becomes clear that He created diverse things, and pairs of every kind. This refutes the claim that He is a single, simple being from whom only one thing proceeds, necessarily inseparable from Him—that nothing else proceeds from Him and that He cannot do anything other than this. For His bringing diverse things into being demonstrates that He acts by His power and will.
For this reason, He says:
“Only those of His servants who have knowledge fear Allah.” (Fātir: 28)
A group of the early generations said: “Those who know Him.” For anyone who regards Him as incapable of bringing about an action or changing anything in the world, but instead holds that He is necessarily bound to something from which He cannot be separated, will not fear Him. Rather, he fears the stars and celestial spheres which, in his view, produce effects on earth, or other things of that kind. This is why these people worshipped them instead of Allah, and why they directed their supplications to them and feared them.