If someone accuses a woman of adultery then he or she must produce four witnesses to corroborate the accusation. Failing that, the woman is innocent, and the accuser is a liar. Calling for four witnesses, protects women against calumny.
The verse in question actually reads: “Why did not those, who gave currency to this charge [of impropriety], bring four witnesses to prove it? Since they have not brought the required witnesses, they are indeed liars in the sight of Allah.” 
This verse, like the preceding verse calling for four witnesses, protects women. If, for example, someone accuses a woman of adultery then he or she must produce four witnesses to corroborate the accusation. Failing that, the woman is innocent, and the accuser is a liar. No other scripture affords women this level of protection against false accusation. Likewise, nothing in the Qur’an or the traditions (Hadith) validates the allegation that a woman must provide four witnesses to prove she was raped.
On the contrary, numerous traditions related to rape also prove that the woman is not to be punished. It is the height of absurdity to suggest that a rape victim faces punishment. Abdul-Jabbar ibn Wa’il ibn Hujr reported on the authority of his father that a woman was raped in the time of Prophet Muhammad(sa). Prophet Muhammad(sa) punished the rapist but prescribed no punishment for the victim . In another tradition, Alqamah ibn Wa’il Kindi reports on the authority of his father that Prophet Muhammad(sa) punished a rapist but not the victim . We challenge critics to cite a Qur’anic verse that prescribes such injustice or a tradition in which Prophet Muhammad(sa) punished the victim but not the rapist.
 Qur’an 24:14.
 Tirmidhi, Book: Punishments, Chapter: On woman who is raped.