194. " the sacred month for the sacred month; and all sacred things are
(under the law of) retaliation.
whoever then commits aggression (by fighting) against you,
attack him in like manner as he attacked you;
and have awe for allah, and know that allah is with the pious ones."

commentary:

according to the islamic calendar, there are four lunar months in
every year which are specifically respected, and fighting is unlawful and
forbidden therein. one month of these four months, i.e., rajab, is
separate while the rest, i.e., zilqa`dah, zil-hajjah, and muharram, are
consecutive. one of the reasons that the month zil-qa`dah is so called
is that in this month it is necessary to have a halt of fighting.

this is the law of islam that enjoins the adherents not to fight
during four particular months of the year, but non-muslim enemies
always lie in ambush to misuse the opportunities. so, they may think
that since muslims are obliged to observe this law, they had better
attack. this verse says that if your opponents rush upon you during
these four months, you can stand against them, too, and fight in the
same months. so, you may apply the sacred month for the sacred
month, because the sanctity of the blood and protection of the system
of islam is much more than the sanctity of these months.

the sacred month for the sacred month, ..."

then, whosoever did not regard with reverences should be treated
under the law of retaliation.

"and all sacred things are (under the law of) retaliation."

hence, as a general rule, it says:

whoever then commits aggression (by fighting) against you, attack him in
like manner as he attacked you;

islam is not a religion of aggression and transgression, but it does
not accept the aggression of others. yet, the style of action should be
in a manner that piety be always observed, and in retaliation, limits
would not be violated when we do know and ought to be aware that
allah is with the pious ones.

"...and have awe for allah, and know that allah is with the pious ones."

explanations:
1- no path is blind in islam. the protection of the unity of islam
and the souls of muslims are preferred to the sanctity of places and
times.

2- we must be equitable even in contact with enemies.

" whoever then commits aggression (by fighting) against you, attack him in
like manner as he attacked you; ..."

3- the necessity of piety, even at the time of fighting, is another
one of the islamic training principles.

4- the order of legislation should not be in a manner that it
becomes a means of despair for muslims and boldness in disbelievers.
the principle of similar reciprocation stands for this very sake.

5- at the time of fighting in similar reciprocation, if you do not
violate the limits of justice and be of the pious ones, you will enjoy of
the divine help.