Wa-in fatakum shay-on min azwajikum ila alkuffari faAAaqabtum faatoo allatheena thahabat azwajuhum (surah Mumtahina: 11)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(60:11) And if you fail to receive from the unbelievers a part of the bridal-due of your disbelieving wives, and then your turn comes, pay to those who have been left on the other side an amount the like of the bridal-due that they have paid. *17 And have fear of Allah in Whom you believe.

Wa in faatakum shai`um min azwaajikum ilal kuffaari fa`aaqabtum fa aatul lazeena zahabat azwaajuhum misla maaa anfaqoo; wattaqul laahal lazeee antum bihee mu`minoon

*17) This thing had two alternatives and the verse applies to both. First, with the disbelievers with whom the Muslims had treaty relations, they wanted to settle the matter, thus: "We shall return the dowers of the women who have emigrated to us, and you will return the dowers of the pagan wives of our men) who have been left on your side." But the disbelievers did not agree to this. However, according to Imam Zuhri, the Muslims, in obedience to the Divine Command became ready to return the dowers of the women who were left behind with the pagans in Makkah, but the pagans refused to return the dowers of the women who had emigrated to the Muslims in Madinah. Thereupon Allah enjoined that the dowers of the emigrant women, which were to be returned to the pagans, should be collected together in Madinah instead of sending these to pagans; then from these collections disbursements should be made to those to whom the dowers were due from the pagans according to what was due to them.
The second alternative was that there were several converts to Islam, who had emigrated to the abode of Islam from the territories of the disbelievers with whom the Muslims had no treaty relations, leaving their pagan wives behind. Likewise, some women also had become converts and emigrated, leaving their pagan husbands behind. About them it was decreed that the matter should be settled in the abode of Islam itself on the bargain basis. That is, when the dowers were not being returned by the disbelievers, no dowers should be returned to them Instead, the dower of the woman who had emigrated to the abode of Islam, should be paid to the person, whose wife had been left with the disbelievers.
But in case the account could not be settled equitably thus, and the amount of the dower due on behalf of the disbelieving wives of Muslims, who were left in the abode of disbelief, exceeded the amount of the dowers of the Muslim women who had emigrated, it was en joined that the deficiency be made up from the spoils that the Muslims took in the wars against the disbelievers. Ibn 'Abbas has related that the Holy Prophet (upon whom be Allah's peace) would command that the loss of the person who did not receive his share of the dower be made up from the spoils. (Ibn Jarir). This same view has been adopted by 'Ata', Mujahid, Zuhri, Masruq Ibrahim Nakha'i, Qatadah, Muqatil and Dahhak. All these scholars say, that the people whose dowers are left with the disbelievers, should be paid these from the collective spoils taken from the enemy. That is, before the booty is distributed, the dead dowers of the people should be paid and then the distribution made in which these people too should be given their equal shares along with the other soldiers. Some jurists say that the loss of such people can be made up not only from the spoils but even from the fai properties But a largo section of the scholars does not subscribe to this view.