This Ayah offers a way out for husbands. If a husband has accused his wife but cannot come up with proof, he can swear the Li`an (the oath of condemnation) as Allah commanded. This means that he brings her before the Imam and states what he is accusing her of. The ruler then asks him to swear four times by Allah in front of four witnesses

﴿إِنَّهُ لَمِنَ الصَّـدِقِينَ﴾

(that he is one of those who speak the truth) in his accusation of her adultery.

﴿وَالْخَامِسَةُ أَنَّ لَعْنَةَ اللَّهِ عَلَيْهِ إِن كَانَ مِنَ الْكَـذِبِينَ ﴾

(And the fifth; the invoking of the curse of Allah on him if he be of those who tell a lie.) If he says that, then she is divorced from him by the very act of this Li`an; she is forever forbidden for him and he must give her Mahr to her. The punishment for Zina should be carried out on her, and nothing can prevent the punishment except if she also swears the oath of condemnation (Li`an) and swears by Allah four times that he is one of those who lied, i.e., in what he is accusing her of;

﴿وَالْخَامِسَةَ أَنَّ غَضَبَ اللَّهِ عَلَيْهَآ إِن كَانَ مِنَ الصَّـدِقِينَ ﴾

(And the fifth; should be that the crath of Allah be upon her if he speaks the truth.) Allah says:

﴿وَيَدْرَؤُاْ عَنْهَا الْعَذَابَ﴾

(But she shall avert the punishment) meaning, the prescribed punishment.

﴿وَيَدْرَؤُاْ عَنْهَا الْعَذَابَ أَن تَشْهَدَ أَرْبَعَ شَهَادَاتٍ بِاللَّهِ إِنَّهُ لَمِنَ الْكَـذِبِينَ - وَالْخَامِسَةَ أَنَّ غَضَبَ اللَّهِ عَلَيْهَآ إِن كَانَ مِنَ الصَّـدِقِينَ ﴾

(if she bears witness four times by Allah, that he is telling a lie. And the fifth; should be that the wrath of Allah be upon her if he speaks the truth.) The wrath of Allah is mentioned specially in the case of the woman, because usually a man would not go to the extent of exposing his wife and accusing her of Zina unless he is telling the truth and has good reason to do this, and she knows that what he is accusing her of is true. So in her case the fifth testimony calls for the wrath of Allah to be upon her, for the one upon whom is the wrath of Allah, is the one who knows the truth yet deviates from it. Then Allah mentions His grace and kindness to His creation in that He has prescribed for them a way out of their difficulties. Allah says:

﴿وَلَوْلاَ فَضْلُ اللَّهِ عَلَيْكُمْ وَرَحْمَتُهُ﴾

(And had it not been for the grace of Allah and His mercy on you!) meaning, many of your affairs would have been too difficult for you,

﴿وَأَنَّ اللَّهَ تَوَّابٌ﴾

(And that Allah is the One Who forgives and accepts repentance,) means, from His servants, even if that comes after they have sworn a confirmed oath.

﴿حَكِيمٌ﴾

(the All-Wise. ) in what He prescribes and commands and forbids. There are Hadiths which explain how we are to put this Ayah into effect, why it was revealed and concerning whom among the Companions it was revealed.