A slave girl which was given as a present to Muhammad by the ruler of Egypt. She became one of Muhammad's concubines.

Muhammad had sexual intercourse with her, on a day that had been promised to Hafsah (or perhaps Aishah), one of Muhammad's proper wifes, and on Hafsah's bed, which caused quite some disturbance among his wives and had further consequences.

Details about this story can be gleaned from these articles: