The perfection and completeness of the Qur'an prove that its validity is not restricted to a particular time or place, since anything perfect is in need of nothing to complete it. In chapter LXXXVI:13-14 God confirms that the Qur'an is a conclusive word" and not a mere "pleasantry." It contains the purest of teachings concerning belief in life-after-death, together with an exposition of the realities of existence, while at the same time, encompassing the fundamentals of correct human behaviour. Since laws governing transactions between men are directly linked to their beliefs, such a book can obviously not be annulled or changed with the passage of time. As He says in XVII:105:
"We have revealed the Qur'an with Truth and it has descended with the Truth," meaning that the revelations and their ongoing validity are inseparable from the Truth. Thus in X:32:
"After the Truth what is there except error,"
And in XLI:41-42:
"In truth it is an unpenetrable book, error may not enter in it from before it or behind it."
In other words the Qur'an repulses, by its own perfection and completeness, any attempt to alter it; and neither now nor later can it be annulled or superseded. Many studies have been made of the permanence of the validity of the laws given in the Qur'an. The reader is advised to consult them if he requires additional knowledge of the subject; to pursue the matter here, (namely, the position of the Qur'an in the lives of Muslims and the manner in which it demonstrates this), would be outside the scope of this book.
source : http://www.maaref-foundation.com