Source: Light within me –by: Imam Khomeini (S.A) - p.124-125
This much can be easily understood by all that all existing things are a sign and a name of Allah. We can say that the whole world is Allah's name. But the case of this name is different from that of the names given to the ordinary things. For example, if we want to indicate a lamp, or a motor car to someone, we mention its name. The same thing we do in the case of man or Zayd. But evidently that is not possible in the case of the Being possessing infinite sublime qualities.

Anything Which is Finite is a Possibly Existing Thing
If an existing thing is finite, it is a possibly existing thing. As Allah's existence is infinite, He should evidently possess all sublime qualities, for if he lacked even one quality, He would become finite and as such possibly existing. The difference between a possibly existing being and an essentially existing being is that the latter is infinite and absolute in every respect. If all the sublime qualities of the essentially existing being were not infinite, that being would not be the essentially existing being and the source of all existence. All the things caused by this source of existence are endowed with the qualities possessed by the essentially existing Being, but on a smaller scale and in varying degrees. What is endowed with these qualities to the utmost possible degree is called the Grand Name or al-ism al-a'zam.

What is the Grand Name?
The Grand Name is that name or sign that is somewhat endowed with all the Divine qualities to the greatest possible degree. As compared to other existing things it possesses the Divine qualities most perfectly, though no existing thing lacks them completely, for everything has been endowed with them according to its nature and capacity. Even those material things which appear to us to be totally devoid of all knowledge and power are not really so and possess some degree of perception and knowledge.

All Existing Things Glorify Allah
As we are veiled, we cannot perceive it. but it is a fact that the sublime qualities are reflected even in the things lower than man and animals. At the most these qualities are reflected in them according to the capacity of their existence. Even the lowest creations possess the quality of perception. The Qur'an says: There is not a thing that does not praise Him, but you do not understand their praise. (Surah Bani Isra'il, 17:44)
As we are veiled and do not understand the praise of all existing things, the ancient scholars did not know that the imperfect beings also possessed perception. that is why they took this praise to mean the praise indicated by the creation of all things, but in fact this verse has nothing to do with that kind of praise, which is quite a different matter as we already know. According to a tradition once the people heard the pebbles in the Holy Prophet's hand praising Allah. They could understand the praise of the pebbles, but this praise was such that the human ears were quite unfamiliar with it. It was in the pebbles' own language, not in any human language. Hence, it is clear that the pebbles possess perception, although of course according to their existential capacity. Man who considers himself to be the source of all kinds of perception, thinks that other things are devoid of it, but that is not a fact, although it is true that man has a higher degree of it. Being veiled, we are unaware of the perception of other things and their praising Allah, and think that there is no such thing.