Zihar
الَّذِينَ يُظَاهِرُونَ مِنكُم
مِّن نِّسَائِهِم (Those of you who declare zihar against their wives...58:2) The aorist yuzahiruna is derived from zihar. There was a cruel custom in pre-Islamic Arabia; as pointed out earlier, where the husband would utter the zihar formula اَنتِ عَلَیِّ کَظَھرِ اُمِّی 'You are to me as my mother's back', and thus she would become permanently and absolutely unlawful to him for cohabitation like the mother. Here the word zahr (back) metonymically refers to bath 'stomach or womb'. [ Qurtubi ]
Definition of zihar and its effect in Shari’ ah
In order to understand the definition of zihar in terms of Shari’ ah, it should be noted first that there are some women who are permanently forbidden for a man, such as mother, sister, daughter and others in the prohibited degree. Although looking at such women is permissible in general, yet looking at some parts of their body is not permissible, (like abdomen, back etc.) Now the definition of zihar is 'to compare one's wife with any of such parts of the body of such prohibited women'. According to the old Arab custom all conjugal relations ceased permanently between a man and his wife when he would use these words; rather it was worse than divorce. In the case of divorce, it was possible to retract and take back the wife. But in the case of zihar, according to the old Arab custom, it was not at all possible to restore the conjugal rights.
The current set of verses brought about reform in the custom in two ways: [ 1] zihar has been declared a sinful act. If a person is placed in a situation where he needs to separate from his wife, he must choose the method of 'divorce'. Zihar should not be resorted to for this purpose, because the utterance of zihar formula is absurd, nonsense and false. Obviously, their wives are not their mothers, the Qur’ an reads thus: مَّا هُنَّ أُمَّهَاتِهِمْ إِنْ أُمَّهَاتُهُمْ إِلَّا اللَّائِي وَلَدْنَهُمْ "...Their mothers are but only those who have given birth to them …58:2] ". The وَإِنَّهُمْ لَيَقُولُونَ مُنكَرًا مِّنَ الْقَوْلِ وَزُورًا further says: "...and undoubtedly they utter an evil word and a lie...[ 58:2] " In other words, their utterance is false, meaning 'calling one's wife mother' is contrary to truth and fact, and also a heinous sin.
[ 2] The second reform the Qur'an brought about is as follows: If an ignorant person or a person unacquainted with the legal formalities of Islam were to utter the zihar formula, his wife does not become permanently unlawful to him, nor does he have an open licence to do as he wishes - like enjoying intimacy with her. The guilty person will have to pay a penalty for uttering such evil, false and obnoxious words. He cannot take back his wife without first paying the prescribed expiation. The following verse prescribes this expiation.