Next Muhammad was a owner of "black" slaves
In Hadith no.436, vol 6, It says: when Umar came to visit Muhammad, he saw a "BLACK SLAVE OF ALLAH'S APOSTLE sitting on the first step" Ibn Qayyim alJawiyya, a great Muslim historian, wrote in his famous book Zad al-Ma'ad (part 1 pg 160): "Muhammad had many male and female slaves. He used to buy and sell them, but he purchased more than he sold, especially after God empowered him by his message, as well as after his immigration from Mecca. He once sold one black slave for two. His name was Jacob al-Mudbir".
He also gives us the names of Muhammad black slaves on pgs 114-116, which were:
Bilal, Abu Hurairah, Usamah Ebn Zaayed, and Rabbah were just a few of the black slaves of Muhammad.
The most famous slave market in Muhammad's day was the slave market in Mecca. Many "blacks" (Hebrews) were stolen from African villages and were auction off like cattle in the same manner as they were in the America's. I must mention here that it was the Arab Muslims that introduce the white European Christians to capturing and selling's "blacks" (Hebrews) on the west coast of Africa, that's why there is similarity between the Arab enslavement of Hebrews ("blacks") in the so called Mid-East and the Christian enslavement of Hebrews ("Blacks") in the west).
Muhammad also mistreated his 'Hebrew slaves". He also said "That if you dreamed of a "black" woman, this was an evil omen (Hadith no 9, vol,162,163). He also referred to black people as "raisin heads" (Hadith no.662, vol 1).
Many believe that Arabs are still buying and selling black slaves today. In the Sudan, Muslims slave markets has been revived as blacks in chains from the Dinka Tribe are now being auctioned off to Muslim masters. In Arabic the common word for black is "Abd" which also means "slave".