24. "Then let man look to his food,"
25. "That We pour down the water, pouring it in abundance,"
26. "And We split the earth into fragments,"
27. "And We produce therein corn,"
28. "And grapes and grasses,"
29. "And the olive and the palm,
30. "And gardens, dense with trees,"
31. "And fruits and fodder,"
32. "Provision for you and for your cattle."
Man should look at his food!
Since the aforementioned verses allude to the Resurrection and the next verses also refer more vividly to this very matter, it seems that these verses are a proof for the Resurrection. By explaining Allah's authority over all things and, also, reviving the dead lands by sending down rain, which is a resurrection in itself for plants, proves the possibility of Resurrection.
By the way, since these verses mention the different kinds of nourishment that Allah has given to Man and his cattle, they call him to thank Allah and pay heed to the knowledge of Him.
First, it says: "Then let man look to his food;" and considers how Allah has produced it.
The closest exterior substance, to Man, is his food which, after some changes, is easily absorbed and becomes part of his body, therefore, if he cannot obtain it he will perish. That is why the Qur'an, among all things, puts emphasis on the nourishment; especially those produced from trees and plants.
It is clear that the aim of saying 'look to' is not a simple look, but it means with deep care and contemplating on the vital elements and wonderful structure of the nourishment, and the surprising effects they have on him, so, consequently, he should think about the Creator, Who has created them.
There is the idea which says that it may mean 'a superficial look, a look which stimulates the salivary glands and, as a result, helps the digestion'. This seems improbable because, in comparison with its pre and post verses, the verse does not carry such a meaning at all; but some food scientists look at the contents of the Qur'an with their own narrow view points, then, it is natural for them to have an idea like that about the verse.
Some others believe it to mean that when one sits at the table to eat, one must look carefully at the foods to see how they are prepared, whether they are permitted or forbidden, lawful or unlawful and, thus, one may consider the moral and religious aspects in eating.
In some narration's from the sinless Imams, the term / ta'am / 'food', here, means 'knowledge', the sustenance of Man's soul, then, one should be careful and 'look' at Whom he has taken it from. Among these is a narration from Imam Mohammad Baqir (p.b.u.h.) for the commentary of the above verse, which says: "Be careful from where and from whom you get your information."
Another narration, similar to this, has been quoted from Imam Sadiq (p.b.u.h.).
Undoubtedly, the apparent meaning of the verse is about the bodily foods which are described in later verses, but the soul's sustenance can analogically be understood from it, since Man is a combination of soul and body; as his body needs bodily food so his soul requires spiritual sustenance, as well.
When Man should be careful about his bodily nourishment, and knows of its origin which, according to the next verses, is life-giving rain, he should also be careful about his spiritual nourishment, the Message revealed from above (like rain) to the Prophet's heart (p.b.u.h.). The very place where the hearts of the sinless Imams got it from and store it like fountains of youth for others to make their own hearts fruitful with faith, virtue and morals.
Yes, one must completely be aware of the main origin of one's knowledge or one may call it 'spiritual nourishment', lest it may come from a corrupted source and, as a result, cause one's soul and body to become sick or die.
And the matter of things being lawful /halal/ or unlawful, /haram/, and permitted or forbidden can analogically be understood through the potential guidance, too.
This is also probable that the terms 'food' and 'look' both have vast meanings in this verse, hence all the three above commentaries can be gathered in it.
It is evident that the term 'man', used in the verse, includes all members of the human race whether they are believers or unbelievers. They must care about what they eat and, also, the wonder of its creation in order for the unbelievers, to find the right way, and for the believers to increase in their faith.
Verily, each article of food: fruits, nutritious seeds, and vegetables have some interesting properties which can be studied, separately, in our lifetime and many things can be learned from them to enlighten us and give us insight into the wonders that they contain.
Then, to explain the nourishment's and their origins, it says:
"That We pour down the water, pouring it in abundance".
The term /sab/ means 'to pour water over from above', and here it means 'sending down rain'. The term /sabba/, at the end of the verse, is used for emphasis and to note the abundance of water.
Water, which is very necessary for every living creature, often comes down sufficiently, because of Allah's grace. And we know that the essential source of water existing in rivers, streams, springs, subterranean canals and wells is rain, so that if it does not rain one year, all of them will dry up.
Thus, while studying articles of food, first and foremost, Man should refer to the importance of the regularity of rainfall. The sun shines over the seas where vapor, in the form of clouds, rises from and moves above the earth where winds scatter the clouds high in the sky. At cold points in the atmosphere, the clouds change into pure, harmless water again and fall gently on the ground in the form of droplets of rain or little pieces of snow that soak into the ground. Trees, plants and living things draw up water from the ground.
After mentioning water, which is an important factor in human life, it refers to another great factor; the earth, and says:
"And We split the earth in fragments".
Many commentators have said that this splitting is the splitting of; the land by plant seeding. It is really wonderful that a little smooth seedling can break the hard, solid land and sometimes it shoots up through stone. What a surprising power the Creator has given to this tiny smooth seedling which enables it to do so!
Some others have said that the split may be the splitting of the land when man ploughs it or even when some worms burrow through it; a kind of plowing for the purpose of some other life activities.
Plowing is one of Man's activities, of course, but Allah has given him all its necessary means, therefore it relates to Allah.
The third commentary, which has been cited for the verse, and seems preferable for certain considerations, says that the meaning of 'splitting the earth' is 'the act of breaking the stone into pieces on the surface of the earth.'
At first the surface of the earth was covered with a mass of stone. Heavy rains fell, continuously, and cleft the stone asunder and spread its little parts onto the low lands and, thus, a mass of agricultural soil was formed, some of which is now carried to the seas by floods. But the new soil, produced by the succeeding rain and snow was replaced by it, otherwise Man would be faced with the lack of agricultural soil.
Then, the verse points to one of the miracles of the Qur'an, in science, when it says it rains, first, then the earth cleaves asunder and becomes fit for farming. This not only happened in the very early days, but also keeps occurring today.
This commentary seems more suitable, because the growth of plants and the production of grains are mentioned in the next verses.
Here, again, all three commentaries, together, can be probable.
After mentioning the two basic factors; i.e. water and soil, it refers to the eight items of plants, which contain the main nutrients for Man and cattle. "And We produce therein corn,".
Corn /habba/ is 'grain, the seeds of cereal grass; wheat, oats, rye or barely, or the plants producing them'. They are the essential sources of Man's and cattle's nourishment's during the year, the lack of which, because of drought, causes famine and starvation, a great plague for the world.
The term /habban/ 'corn', in a general sense, shows the importance and the variety of the seeds. Some others have only meant it as 'wheat' or 'rye' which is not reasonable, because the term 'corn' can include all seeds, which was mentioned before.
"And grapes and grasses"
The term /'inab /, which means both 'grapes and vine', in the verses of Qur'an, is mentioned, here, because it contains many nutrients, as a complete food and more than other fruits. It means only grapes in this verse.
The term /qaDb/ originally means 'the vegetables which are cut several times', and, here, it means the different kinds of vegetables. Its occurrence after the term 'grapes' is for its importance as a food material.
Today, vegetables enjoy a high position in food science and are especially recommended.
The term /qaDb/ is sometimes used with the meaning of 'to cut, or to pick'.
It is probable that /qaDb/, used, here, in this verse, has a broader meaning which includes both vegetables and fruits.
"And the olive and the palm".
It is clear that these two items are both from the most important articles of food which are useful, sound, and nutritious. This is why they are mentioned and emphasized on, here.
"And gardens, dense with trees".
The term / hada'iq / is the plural form of / hadiqah / which is 'a garden surrounded by a wall', but originally it means 'a piece of land containing water for irrigation'. The word is derived from /hadaqah/ 'eye-socket' where water exists, constantly.
Since these kinds of gardens are usually fruit gardens, the word may hint to the kinds of fruits in Heaven.
The term /qulb/ is the plural form of /aqlab/ and /qulba '/ which means 'thick-necked' and is originally derived from /qalabah/. Here, it means 'tall, thick trees'.
"And fruits and fodder".
The term /abb/ means 'herbage not sown by men' or 'herbage prepared for pasture and for cutting'. Basically it means 'preparation' and, since these pastures are prepared for the usage, so, they are called /abb/.
Some others have also said that /abb/ is used for the fruits that are suitable for drying and storing to be used in winter, because they are always ready for use.
The late Mufid in his book, Irshad, has narrated from Amir-al-Mo'mineen Ali (p.b.u.h.) that the word meant 'herbage as a pasture', and he added: "What Gad said in the verse 'And fruits and fodder' is a divine gift for His servants that He created as a part of their food and for their cattle, from which their lives receive merit and their bodies are strengthened". 
In the former verses some special fruits were named, while here fruits, in general, are discussed. Moreover, the last verse spoke about 'gardens', which seemed to mean 'the fruits of gardens', then, how are the fruits dealt with, here, again?
The answer to this question is this: There, some definite fruits such as grapes, olives, and dates, which are of great importance among all fruits, were named; but, here, fruits are mentioned separate from 'gardens', perhaps because, besides fruits, gardens have some more advantages, such as, fresh air, nice views, etc.
Moreover, the leaves of some trees and the twigs, the roots, and the barks of some others (for example: tea, cinnamon, ginger and the like) are among the edibles; in addition to the leaves of many trees, which are suitable food for cattle. And it is a fact that the items stated in the aforementioned verses are edible for both human beings as well as their cattle.
For this reason, in the next verse, it says:
"Provision for you and for your cattle."
The term / mata'/ means 'anything that Man uses or enjoys'.
There are eight nutriments named, in these verses, for Man and cattle. It is interesting that all of them are from herb ages and that is because of the importance of vegetables, grains and fruits in Man's diet, so, in other words, they are the true original nutriments, while meat, obtained from animals, is in the second position and in a lesser amount.
Also noteworthy is that food science, which is one of the wide spread and important sciences and has a broad field with a large scope of investigation, is an explanation for what is mentioned in these verses and shows the magnificence of the Holy Qur'an, especially when this science emphasizes on the value and the efficiency of these food materials.
In any case, taking note of these materials and thinking about the creator of them may cause Man's awareness of Allah's grace and mercy to Mankind.
Yes, paying attention to ones bodily food and, then, the sustenance of the soul from the points of both its structural content and how one obtained it, can push one forward along the path of knowledge of Allah, righteousness, and self-perfection. Verily, "Then let man look to his food", and what a meaningful sentence this short, single statement is!
 The term /fal-yanzur/ my originally mean that 'if Man is in doubt of his Creator and the Resurrection, then let him look to his food'.
 Irshad-i-Mufid, From Al-Mizan, vol. 20, p. 319.