Third:

His statement that any of their slaves who emigrates becomes free and enjoys the same rights as the other emigrants, as in the account of Abū Bakra and the slaves belonging to the people of al-Tā’if who emigrated with him. There is no doubt about this: by embracing Islam and emigrating, he gains ownership of his own person. The property of those at war with the Muslims is open to lawful appropriation, so whoever gains possession of something becomes its owner. If he gains control over his own person, he is all the more entitled to own it, and Islam safeguards that ownership.

Fourth:

When a slave belonging to people bound by a treaty emigrates, his owners are compensated for his value, but the slave himself is not returned, because their property is protected. This is comparable to the case of a slave belonging to a non-Muslim under Muslim protection who embraces Islam: the owner is ordered to relinquish ownership of him by selling him, giving him away, or setting him free. If he complies, well and good; otherwise, the slave is sold on his behalf. The slave himself is not returned to them, because they would hold a Muslim in slavery, which is impermissible.

This differs from returning a free man to them, since they do not enslave him. Thus, when the Prophet, may Allah bless him and grant him peace, stipulated that women should be returned along with men, Allah annulled that stipulation and commanded him not to return Muslim women, saying:

“Neither are these women lawful for those men, nor are those men lawful for them.”

For among the unbelievers, liberties are permitted with a Muslim woman that are not permitted with a man, since a captive woman is like a captive man. Allah commanded him to return the dowry as compensation.