Verse 21, Surah Al Hijr

وَاِنۡ مِّنۡ شَىۡءٍ اِلَّا عِنۡدَنَا خَزَآئِنُهٗ وَمَا نُنَزِّلُهٗۤ اِلَّا بِقَدَرٍ مَّعۡلُوۡمٍ‏

Wa-in min shay-in illa AAindanakhaza-inuhu wama nunazziluhu illa biqadarinmaAAloom

And there is not a thing but that with Us are its depositories, and We do not send it down except according to a known [i.e., specified] measure.