Tafsir of Al-Mu'minoon 23:21

"And indeed, for you in grazing livestock is a lesson." This is an exposition of the blessings reaching them by way of animals, following the exposition of the blessings flowing from water and vegetation. It has been made clear that, while they are blessings in themselves from which they derive various benefits, they are also a "lesson" from which they must learn, using the circumstances surrounding them as evidence for the immense power of Allah—Exalted and Majestic is He—and His abundant mercy, so that they may give thanks to Him and not disbelieve. This is specifically attributed to livestock because the potential for a lesson is most manifest within them.

As for His saying, "We give you to drink of that which is in their bellies," this is a detailing of the aspects of the lesson found within them. That which is in their bellies refers either to milk—in which case the particle min (from) indicates partition, and "bellies" refers to the interiors, for the milk is in the udders—or it refers to the fodder from which the milk is formed—in which case min indicates origin, and "bellies" is taken literally. In either case, the pronoun in "their bellies" refers to the livestock, considering the attribution of the part to the whole, rather than to the females specifically by way of istikhdam (using a pronoun to refer to a different aspect), for the generality of what follows rejects that. It has been recited with a fat-ha on the nun (tasqikum) and with a ta (tasqikum), meaning: the livestock gives you to drink.

"And for you therein are many benefits": other than what has been mentioned, such as their wool, their hair, and their fur.

"And from them you eat."

The apparent meaning is that "eating" is used in its literal sense, and min is for partition, because some parts of the livestock are not eaten. The prepositional phrase is placed first for the sake of the verse’s rhythmic ending, or for a relative restriction in comparison to donkeys and the like, or a restriction regarding the connotation of "you eat" implying a continuous habit. This serves as an explanation of their benefit from the entities of the animals themselves, while what preceded it was an explanation of their benefit from the utilities and products derived from them. It is possible in my view—though I have not seen anyone state it explicitly—that "eating" could be metaphorical or a metonymy for "obtaining sustenance" generally, as you heard before; meaning: and from them you are provided for and obtain your livelihoods.