it is permissible for the Muslim to marry a woman from the People of the Scripture - a Christian or a Jew - if she is a chaste woman. The basic evidence for this permissibility is the Saying of Allah (Exalted be He),
Made lawful to you this day are At-Tayyibât [all kinds of Halâl (lawful) foods, which Allâh has made lawful (meat of slaughtered eatable animals, milk products, fats, vegetables and fruits)]. The food (slaughtered cattle, eatable animals) of the people of the Scripture (Jews and Christians) is lawful to you
and His Saying,
...and chaste women from those who were given the Scripture (Jews and Christians) before your time when you have given their due Mahr (bridal-money given by the husband to his wife at the time of marriage), desiring chastity (i.e. taking them in legal wedlock) not committing illegal sexual intercourse, nor taking them as girl-friends.
(Part No. 18; Page No. 319)
In Arabic the word Muhsanat (casually translated in the Ayah as 'chaste women' ) implies the qualities of chastity and freedom. As regards the Saying of Allah (Exalted be He),
And do not marry Al-Mushrikât (idolatresses, etc.) till they believe (worship Allâh Alone).
, it is about the idolatress women and not the women of the People of the Scripture; because the Qur'anic Ayah from Surah Al-Ma'idah is clear about the lawfulness of marrying women from the People of the Scripture.
the basic source for slavery is prisoners of war who are captured by Muslims through wars between them and the unbelievers and through Jihad (fighting in the Cause of Allah) to make the word of Allah (Exalted be He) superior and to defend His Religion. This status applies to the descendants who are born into slavery and they cannot be released except through manumission. On the other hand, kidnapping free persons to be sold into slavery is not permissible. Also, it is not permissible for a Muslim to enslave another Muslim captured through wars between Muslims or to sell a free Muslim. None of this is permissible and it is even unlawful; it does not prove ownership of the slave in question. If enslavement takes place through the legal means we mentioned, it is permissible for the Muslim to purchase slaves, which includes female slaves as mentioned by the questioner. (Part No. 18; Page No. 320) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.