You have raised some questions which require detailed answers. The constraints of this forum do not allow me to go into details in regards to contexts of such rules.

 

All that I can do here to mention a few things:

 

1. It is important for us to consider the evolutionary nature of Islamic laws: The Qur’an is the only scripture in the world that sets out clearly abolition of slavery as a divine dictum. It has been explicitly stated even in the Makkan revelations before all other laws came into effect in Madinah.

 

Thus there were certain practices – tolerated earlier –  forbidden later. An obvious example is the prohibition of alcohol; it was condoned earlier and was prohibited stages. Another case – relevant to the issue at hand – is the prohibition of various forms of male and female union practiced in Arabia and all over the world before Islam; Islam disallowed all of them except the marriage that exists today.

 

Allowing sexual intimacy with the female slaves was one such form of marriage prevailing among the Arabs as well as Jews. It was in the same manner that Prophet Ibrahim took Hagar as his wife. God forbid it was not an adulterous union or fornication; rather a valid form of union between man and woman allowed in those times. It came with certain responsibilities; for instance, that the child born from the union inherits the father and the mother becomes free she gives birth.

 

2. The Prophet (peace be upon him) ought to be judged by his life and mission; he was allowed certain things by Allah to unite various tribes; his marriages with most of his wives were clearly intended to unite the various tribes and ethnicities. He married Safiyyah who was of a Jewish background also with the same purpose in mind. They were all freed.

 

Likewise, all of the slaves who came into the hands of the Prophet were all freed before he died. His companions also followed his example; that is why we find some of them freeing hundreds of slaves. So, never judge the Prophet (peace be upon him) by the secular or agnostic standards of those who blinded by their distorted perspective on Islam.

3. All those women who were taken as slaves became gradually freed and from them came generations of Muslims who became eminent scholars of Islam:: an example is Muhammad b. Ka`ab al-Qurazi who descended from the Jewish clan of Banu Quryazah.

 

4. Mariyah was one of the wives of the Prophet (peace be upon him); she bore him his son Ibrahim. Her case is comparable to the relationship of Hagar to Prophet Ibrahim (peace be upon him). Hagar was one of the wives of Prophet Ibrahim and the mother of Prophet Isma`eel. There is no difference between the two cases, whatsoever.

 

5. The laws of intimacy with the prisoners of war do not apply now as the entire slavery system has been entirely abolished once and for all. And the Prophet (peace be upon him) said, “Allah will not look at a person who takes a free person and makes him a slave!”

 

6. As for the last question, you could refer to some Qur’anic commentaries such as those of Muhammad Asad or Yahya Emerick.

Almighty Allah knows best.