Source: "The Miracles of the Qur'an" Shaykh M Mitwalli Al-Sharawi.

The language of the Qur’an is unsurpassed in its accuracy of meaning and
expression. Each letter and word has its place while the language is free from
fault. These unique features are found manifested in the use of one single letter
or a preposition, as is demonstrated in the following verses:

Ya bunayya aqimi alssalata wa/mur bialmaAAroofi wainha AAani almunkari
waisbir AAala ma asabaka inna thalika min AAazmi al-omoori

“...and bear patiently that which befalls you; surely these acts require courage;”
(Qur’an 31:17)

Walaman sabara waghafara inna thalika lamin AAazmi al-omoori

“And verily whoso is patient and forgiveth - lo! that, verily is (of) the steadfast
heart of things.”(Qur’an 42:43)

In the second verse the preposition “of” (LAMIN) may pass unnoticed or be taken
as an emphatic synonym. But this is not so, because every letter or word in the
language of the Qur’an is selected with the utmost care to convey one intrinsic
meaning and definite purpose. There is no such thing as synonymity in the
Qur'an. Each letter and word has its own fixed meaning which no other word can
express as accurately, irrespective of their seeming similarity. If we consider
thoughtfully the meticulous selectivity of the words in the above verses and their
underlying meaning, we soon come to realize that there are two kinds of
patience. In the first kind there is no direct adversary or person responsible for
hardship or misfortune; for example a brick falling from a building under
construction onto the head of an unsuspecting pedestrian, or the collapse of a
newly- built house over peacefully sleeping tenants. In all incidents and mishaps
of this nature no individual bears the responsibility for the victim’s misfortune. It
is therefore easy for the unfortunate man to restrain his anger and accept his
misfortune as an act of Allah. This kind of patience does not require a great deal
of energy and can be easily achieved. But patience which is “ verily of the
steadfast heart of things “ is that which involves an antagonist against whom a
victim has the freedom to retaliate and avenge himself, but prefers to suppress
his anger and vengeful tendencies and forgive him. This kind of patience is
deemed by Allah to be worthier than the first, because in this kind the aggrieved
is dominated by his instinctive anger and feelings of injustice, and has to exercise
a great deal of self-restraint. He is restrained by his fear of Allah, and refrains
from responding to evil with evil. In the above verses, Allah defines the merits of
the two types of patience and their corresponding heavenly rewards. He also
describes the human responses of retaliation that ought to be observed in each
case by the faithful. Thus, in the first case they are commanded to accept what
befalls them with humility and resignation to His will. In the second they are
commanded to be forgiving and to maintain their faith in Allah’s justice.

The preposition ‘of’ has obviously been used to accentuate the distinction
between the kind of patience in which forgiveness is not a necessity, and that in
which forgiveness represents a test of endurance of injustice and of the believer’s
trust in Allah’s providence and will. This shows how a single letter or preposition
can bear such dept of meaning and discriminating power in the language of the
Qur’an.