Tafsir of Al-Hijr 15:21

"And there is not a thing..."

The mention of "the treasuries" is a metaphor. The meaning is: There is nothing from which the servants benefit except that We are capable of bringing it into existence, forming it, and bestowing it as a favor. We do not grant it except in a known measure, which We know to be in their best interest. Thus, the treasuries were used as a metaphor for His power over everything that is capable of being brought into existence.

"And We have sent the winds as fertilizing agents, and We have sent down water from the sky, and We have given it to you to drink, and you are not its keepers."