Allah's statement,

[لاَ هُنَّ حِلٌّ لَّهُمْ وَلاَ هُمْ يَحِلُّونَ لَهُنَّ]

(They are not lawful for the disbelievers nor are the disbelievers lawful for them.) This Ayah forbids Muslim women for idolators, which was a lawful marriage in the beginning of Islam. Abu Al-`As bin Ar-Rabi` was married to Zaynab, the Prophet's daughter. She was a Muslim, while Abu Al-`As was still an idolator like his people. When he was captured during the battle of Badr, his wife, Zaynab, sent his ransom, a necklace that belonged to the Prophet's first wife Khadijah. The Prophet became very emotional when he saw the necklace and said to the Companions,

«إِنْ رَأَيْتُمْ أَنْ تُطْلِقُوا لَهَا أَسِيرَهَا فَافْعَلُوا»

(If you decide to set free the prisoner who belongs to her, then do so.) They did, and Allah's Messenger set him free. His ransom was that he send his wife to Allah's Messenger . Abu Al-`As fulfilled his promise and sent Zaynab to Allah's Messenger along with Zayd bin Harithah. Zaynab remained in Al-Madinah after the battle of Badr, which took place in the second year of Hijrah, until her husband Abu Al-`As bin Ar-Rahi` embraced Islam in the eighth year after the Hijrah. She returned to their marriage without renewing the dowery. Allah's statement,

[وَءَاتُوهُم مَّآ أَنفَقُواْ]

(But give them that which they have spent. ) meaning, the husbands of the emigrant women who came from the idolators, return the dowery that they gave to their wives. This was said by Ibn `Abbas, Mujahid, Qatadah, Az-Zuhri and several others. Allah's statement,

[وَلاَ جُنَاحَ عَلَيْكُمْ أَن تَنكِحُوهُنَّ إِذَآ ءَاتَيْتُمُوهُنَّ أُجُورَهُنَّ]

(And there will be no sin on you to marry them if you have paid their due to them.) means, when you wish to marry them, then give them their dowery. That is, marry them under the condition that their `Iddah (waiting period) is finished and they have a legal guardian for their marriage etc. Allah said,

[وَلاَ تُمْسِكُواْ بِعِصَمِ الْكَوَافِرِ]

(Likewise do not keep disbelieving women,) thus forbidding His faithful servants from marrying idolator women or remaining married to them. In the Sahih, it is recorded that Al-Miswar and Marwan bin Al-Hakam said that after the Messenger of Allah conducted the treaty with the Quraysh idolators at Al-Hudaybiyyah, some Muslim women emigrated to him and Allah the Exalted sent down this Ayah about them,

[يأَيُّهَا الَّذِينَ ءَامَنُواْ إِذَا جَآءَكُمُ الْمُؤْمِنَـتُ مُهَـجِرَتٍ]

(O you who believe! When believing women come to you as emigrants) until,

[وَلاَ تُمْسِكُواْ بِعِصَمِ الْكَوَافِرِ]

(Likewise do not keep disbelieving women,) Then `Umar bin Al-Khattab divorced two of his wives, who were idolatresses, and one of them got married to Mu`awiyah bin Abi Sufyan, while the other got married to Safwan bin Umayyah. Ibn Thawr narrated that Ma`mar said that Az-Zuhri said, "This Ayah was revealed to Allah's Messenger while he was in the area of Al-Hudaybiyyah, after making peace. He agreed that whoever comes from the Quraysh to his side, will be returned to Makkah. When some women came, this Ayah was revealed. Allah commanded that the dowery that was paid to these women be returned to their husbands. Allah also ordered that if some Muslim women revert to the side of the idolators, the idolators should return their dowery to their Muslim husbands. Allah said,

[وَلاَ تُمْسِكُواْ بِعِصَمِ الْكَوَافِرِ]

(Likewise do not keep disbelieving women).'' Allah's statement,

[وَاسْـَلُواْ مَآ أَنفَقْتُمْ وَلْيَسْـَلُواْ مَآ أَنفَقُواْ]

(and ask for that which you have spent and let them ask for that which they have spent.) means, ask them for what you have paid to your wives who reverted to the side of the idolators, and they are entitled to get back the dowery that they gave their wives who emigrated to the Muslims. Allah's statement,

[ذَلِكُمْ حُكْمُ اللَّهِ يَحْكُمُ بَيْنَكُمْ]

(That is the judgement of Allah, He judges between you.) means, this judgement about the treaty and excluding women from its clauses, is a decision that Allah made for His creatures,

[وَاللَّهُ عَلِيمٌ حَكِيمٌ]

(And Allah is All-Knowing, All-Wise.) meaning, He knows what benefits His servants and is the Most Wise about that. Allah the Exalted said,

[وَإِن فَاتَكُمْ شَىْءٌ مِّنْ أَزْوَجِكُمْ إِلَى الْكُفَّـرِ فَعَـقَبْتُمْ فَآتُواْ الَّذِينَ ذَهَبَتْ أَزْوَجُهُمْ مِّثْلَ مَآ أَنفَقُواْ]

(And if any of your wives have gone from you to the disbelievers -- then you succeeded (gained victory) over them; then pay those whose wives have gone, the equivalent of what they had spent.) Mujahid and Qatadah explained this Ayah, by saying, "This is about the disbelievers who did not have a treaty of peace. If a woman flees to the disbelievers and they do not give back what that her husband spent on her, then if a women comes to them (the Muslims) they are not to return to her husband anything until they pay the Muslim whose wife went to them the equivalent of what he spent. '' Ibn Jarir recorded that Az-Zuhri said, "The believers abided by Allah's decree and paid what they owed the idolators to compensate for the dowery the idolators gave to the women (who emigrated). However, the idolators refused to accept Allah's judgement for what they owed the Muslims. Allah said to the faithful believers,

[وَإِن فَاتَكُمْ شَىْءٌ مِّنْ أَزْوَجِكُمْ إِلَى الْكُفَّـرِ فَعَـقَبْتُمْ فَآتُواْ الَّذِينَ ذَهَبَتْ أَزْوَجُهُمْ مِّثْلَ مَآ أَنفَقُواْ وَاتَّقُواْ اللَّهَ الَّذِى أَنتُمْ بِهِ مُؤْمِنُونَ ]

(And if any of your wives have gone from you to the disbelievers -- then you succeeded (gained victory) over them; then pay those whose wives have gone, the equivalent of what they had spent. And have Taqwa of Allah, the One in Whom your are believers.) Therefore, if a Muslim woman reverts to the idolators, the believers should give back the dowery her Muslim husband paid her, from whatever money is left with them from the dowery of women who migrated to the Muslims. They were supposed to return this wealth to the idolator husbands of these emigrant women. If they still have anything they owed the idolators, then they should return it to them.''

[يأَيُّهَا النَّبِىُّ إِذَا جَآءَكَ الْمُؤْمِنَـتُ يُبَايِعْنَكَ عَلَى أَن لاَّ يُشْرِكْنَ بِاللَّهِ شَيْئاً وَلاَ يَسْرِقْنَ وَلاَ يَزْنِينَ وَلاَ يَقْتُلْنَ أَوْلْـدَهُنَّ وَلاَ يَأْتِينَ بِبُهُتَـنٍ يَفْتَرِينَهُ بَيْنَ أَيْدِيهِنَّ وَأَرْجُلِهِنَّ وَلاَ يَعْصِينَكَ فِى مَعْرُوفٍ فَبَايِعْهُنَّ وَاسْتَغْفِرْ لَهُنَّ اللَّهَ إِنَّ اللَّهَ غَفُورٌ رَّحِيمٌ ]

(12. O Prophet! When the believing women come to you pledging to you that they will not associate anything with Allah, and that they will not steal, and that they will not commit Zina, and that they will not kill their children, and that they will not utter slander, fabricating from between their hands and their feet, and that they will not disobey you in Ma`ruf (good), Allah said to the faithful believers,

[وَإِن فَاتَكُمْ شَىْءٌ مِّنْ أَزْوَجِكُمْ إِلَى الْكُفَّـرِ فَعَـقَبْتُمْ فَآتُواْ الَّذِينَ ذَهَبَتْ أَزْوَجُهُمْ مِّثْلَ مَآ أَنفَقُواْ وَاتَّقُواْ اللَّهَ الَّذِى أَنتُمْ بِهِ مُؤْمِنُونَ ]

(And if any of your wives have gone from you to the disbelievers -- then you succeeded (gained victory) over them; then pay those whose wives have gone, the equivalent of what they had spent. And have Taqwa of Allah, the One in Whom your are believers.) Therefore, if a Muslim woman reverts to the idolators, the believers should give back the dowery her Muslim husband paid her, from whatever money is left with them from the dowery of women who migrated to the Muslims. They were supposed to return this wealth to the idolator husbands of these emigrant women. If they still have anything they owed the idolators, then they should return it to them.''