Tafsir of Al-Mu'minoon 23:18

{بقدر} By a measure (bi-qadar): A measure through which they are safe from harm and attain benefit. Or, according to the measure of what We know of their needs and interests.

{فأسكناه في الأرض} "And We settled it in the earth": Like His saying: "And caused it to travel as springs in the earth" (Az-Zumar: 21). It is said: We made it stationary in the earth.

It is also said: These are the five rivers: Sayhun (the river of India), Jayhun (the river of Balkh), the Tigris and Euphrates (the rivers of Iraq), and the Nile (the river of Egypt). God sent them down from a single spring among the springs of Paradise, deposited them in the mountains, caused them to flow through the earth, and placed in them benefits for people in their various livelihoods.

Just as He is capable of sending it down, He is capable of raising it and removing it.

{على ذهاب به} "To take it away": This is among the most indefinite of indefinite nouns and the most incisive in its articulation. The meaning is: by any manner of taking it away and any path thereof. It signals the absolute power of the One who takes it away, and that nothing is difficult for Him if He wills it. This is more eloquent in its warning than His saying: "Say, 'Have you considered: if your water was to become sunken [into the earth], then who could bring you flowing water?'" (Al-Mulk: 30).

Therefore, servants must revere the blessing of water, bind it with constant gratitude, and fear its departure if it is not appreciated.

{فأنشأنا لكم به جنات من نخيل وأعناب لكم فيها فواكه كثيرة ومنها تأكلون * وشجرة تخرج من طور سيناء تنبت بالدهن وصبغ للأكلين}