Tafsir of Al-Qamar 54:28

"And inform them that the water is shared between them; every share of drink is attended [by its turn]."

Inform them that the water of the well which belongs to them is divided between them—a day allotted to it [the she-camel] and a day allotted to them. The use of "between them" (instead of "between it and them") is to prioritize the rational beings [in linguistic expression]. Mu‘adh narrated from Abu ‘Amr the reading qasamah with a fatḥah on the qāf.

"Every share of drink is attended": meaning a portion and a share thereof is attended by its owner during his turn. Thus, the she-camel attends it at one time, and they attend it at another. It is also said that it means others move away from it, derived from the phrase "he attended away from such-and-such," meaning he moved away from it. It is further said that it means others are prevented from it, as a metaphorical usage of the word ḥaẓr (prohibition) with the letter ẓā’, based on the relationship of causality, for it is caused by the presence of its owner during his turn—though this is as you see [i.e., questionable]. Another view is that they attend the water during their turn, and the milk during her turn. The meaning is: every portion of water and milk, you are those who attend it.